It is a characteristic

near Port Dalhousie, on mud between tidemarks. Assiminia, though much shorter and rounder than the Bengal species A. Francesi, Gray, and belonging in fact to a different section of the genus. It is closely allied to some Singapore species and also to A. marginata, Leith, which inhabits Bombay, but may be distinguished from all by the double marginal impressed line below the suture.

The animal is deep red, with a black spot upon each of the lobes into which the proboscis is divided. The eyes are at the top of the short tentacles.

Family RISSOIDÆ.
IRAVADIA, n. g.

Testa imperforata, turrita, spiraliter costata, solida, epidermide tecta : apertura ovata, integra, antice obsolete effusa; peristomate recto, extus variciformi-incrassato, intus dilatato.

Animal? Operculum?

Shell imperforate, turrited, spirally ribbed, rather thick, covered with an epidermis. Aperture ovate, without a canal, slightly effnsə in front; peristome straight, not sinuate, with an external varix, and slightly expanded within. Animal and operculum unknown. No. 13, Iravadia ornata, n. sp. Pl. II. fig. 13. 14.

Testa turrita, decollata, subcylindrica, (junior elongato-conica), solida, spiraliter costata, inter costas confertim verticaliter costulata, sub epidermide olivaceá vel ferrugineá albida. Anfr. superst. 3-4, rotun-dati, superi tribus, penultimus quatuor, ultimus sex costis spiralibus ornati, hoc juxta aperturam paulo ascendente. Apertura sub-verticalis, elliptica, intus alba, (in testâ juniori postice angulata), antice subangulata et in testá adultá obsolete effusa, in juniori subcanaliculata ; peristoma extus incrassatum, nodoso-variciforme, nodis costis spiralibus congruentibus, intus vix expansum. Operc.?

Long. 41, diam. 21 mill.

Shell turrited, decollated (the young shell elongately conical,) thick, spirally ridged, with close vertical costulation between the ridges, white, with a brownish or olive epidermis. Whorls apparently about 6, when perfect, but only 3 or 4 remain in all the specimens collected; body whorl with 6 spiral ribs, of which 4 only appear on the penul timate whorl, and 3 on the upper whorls, the lower ribs being concealed. On all the upper whorls the 2nd and 3rd ridges are the

are less strong

strongest. Those near the suture, both above and below, ly marked, and are occasionally obsolete. On the last whorl the uppermost ridge near the suture is alone fainter than the others. The body whorl ascends a little towards the aperture, which is subvertical and nearly elliptical. The anterior canaliculation is obsolete in the adult, but it is well marked in the young shell. Peristome much thickened, externally variciform, the varix being nodose in consequence of the spiral ribs of the body whorl being continuous upon it. In young specimens the lip is grooved inside, the grooves corresponding to the external ribbing, and slight remains of this grooving may be traced in the adult shell.

I had at first classed this shell as a Rissoina on account of the obsolete canal, although it differs in essential characters from any species of that genus. I am indebted to my friend Dr. Stoliczka for calling my attention to the great distinctions which exist between the present form and Rissoina, and some of which equally serve to distinguish it from Rissoa and all other genera of the group. Iravadia differs from Rissoina in possessing an epidermis, in having spiral sculpture, in the peristome neither being sinuate above, nor projecting below, and in the columellar margin being simply curved in front and not excavated. From Rissoa it is distinguished also by its epidermis and sculpture, by the obsolete channel in front of the aperture, which, in young specimens, is quite as distinct as in Rissoina, and by the absence of any tendency to the columellar tooth or fold, which is so conspicuous in the typical species of the genus. The characters of the sculpture, epidermis, and aperture serve equally to separate the present form from Alvania, Onoba, Ceratia and other genera of Rissoida: Hydrobia and Amnicola alone have an epidermis, but both are smooth shells without a variciform peristome.

It is unfortunate that no specimen of the operculum has been preserved. The few shells found were collected during a hurried journey in a boat. The species was only met with at one spot, under stones, amongst some rocks in a creek leading into the Myittaya, a branch of the Bassein river. Several specimens were obtained, but when an opportunity was afforded of examining them at leisure, the opercula had disappeared. In the absence of the operculum, I should be disposed to consider the genus as more nearly allied to Rissoina than to

any other, and such naturalists as may refuse generic rank to Iravadia, may perhaps best class it as a subgenus or section of that genus. It may have affinities with a curious species from Peru (Rissoina sulcifera, Trosc.) figured by Schwarz von Mohrenstern in his monograph of Rissoina in the Denksch. k. k. Akad. Wien, xix, 182, Taf. 10, fig. 83, and the differences between which and all other Rissoinæ are pointed out by that author.

The curious little shell dredged by Mr. A. Adams in the seas of Japan and described by him as Vanesia sulcatina in the Annals and Magazine of Natural History for 1861, Ser. 3, vol. viii, p. 242, may also possibly have some affinities with Iravadia.

No. 14, Stenothyra monilifera, Bens. Pl. II, fig. 15.

I found two specimens of this species at Port Dalhousie in the Bassein river. The type was first obtained by Mr. Theobald at Mergui and Rangoon, and the shell has since been found in Cochin China. As the species does not appear to have been figured, I add an illustration of it.

Family NERITINIDÆ.

No. 15, Neritina Peguensis, n. sp. Pl. I. fig. 1—16.

Testa globosa, oblique ovalis, solida, confertim oblique subsinuate rugata, interdum spinigera, epidermide fusco-olivaced, minute flavo punctulata, aliquando maculis oblongis subcurvatis flavis infra suturam ornatá, vel fasciis subobsoletis spiralibus circumdatá, induta, sub epidermide cærulea vel rubella, albido-maculata. Spira vix exserta, plerumque erosa, sutura elevato-compressa. Anfr. circa 3, superi pla nulato-concavi, ultimus superne ad suturam appressus, supra peripheri am aut carinatus, spinisque distantibus munitus, vel obsolete angulatus, subtus rotundatus. Apertura intus lactea; peristoma semiovale, areá columellari planulatá, luteolá v. sordide albida, minute denticulatá, plica unica majori intrante supramedianá munitá, antice edentatâ, Operc. extus planum, albidum, margine externá nigrâ, intus rubrum. Maj. diam. 19, min. 15, alt. 19 mill. Hab. in rivulo ad Promontorium Negrais.

Var. minor testá magis rotundatá, spinis omnino carentibus, fig. 13-16. Maj. diam. 14, min. 11, alt. 15 mill.

Hab, ad Portum Dalhousie.

Shell globose, obliquely oval, solid, closely obliquely and rather sinuously wrinkled, sometimes bearing spines, covered with a dark epidermis. Colour generally dark olive with minute yellow specks, occasionally with oblong splashes of yellow below the suture; these generally curve backwards, and are sometimes, but rarely, of large size. Some shells are surrounded more or less obsoletely with yellow bands. Beneath the epidermis the shell is pink or bluish spotted with white. Young specimens are frequently pink, with yellow specks, in front of each of which is a black streak like a shadow. The spire is barely exserted, apex obtuse, and generally eroded, the erosion extending frequently down the spire, and often a portion of the outer surface of the last whorl itself is wanting; suture raised, compressed. Whorls 3, the upper ones frequently wanting, but when present, flattened or subconcave. Last whorl concave and compressed against the suture above, then either carinate above the periphery and bearing short subdistant spines, or else obtusely, more or less obsoletely angulate. Below it is always rounded. Aperture milky within, peristome semioval, columellar area flat, yellow or dirty white, minutely denticulate, except in front, and having a prominent re-entering tooth just above the middle. Operculum pinkish white outside, exterior margin black, red inside.

The nearest ally to this form with which I am acquainted in N. obscurata, Recluz, which has a more expanded mouth, and more deeply emarginate columellar area, the whorls appear also rather differently shaped above.

The present species is eminently variable. The type occurred in abundance close to the beach in a small stream which descends from the hills close to Cape Negrais; specimens were especially abundant in a brackish pool at the beach, spinous and spineless shells occurred mixed together, and the presence or absence of spines is evidently of no importance. The spineless variety from Port Dalhousie was found in the salt water of the Bassein river, abounding along the strand between tide marks.

To illustrate the variation of this species, several specimens have been figured.

Specimens collected by Mr. Theobald in Arakan illustrate the gradual passage, by absolutely insensible gradations, of this form, into the very distinct N. retifera, Bens. of the Ganges delta.

No. 16, Neritina obtusa, Benson.

Scarce. I obtained two specimens on limestone rock at Thamandewa in the Bassein river.

No. 17, Neritina Smithii Gray.

Less common than in the estuary of the Ganges.

I have another species of Neritina belonging to the typical section from the estuary of a small stream running into the sea just north of Cape Negrais. I have been unable to identify it with any known species, and it may possibly be new.*

No. 18, Neritina (Dostia) depressa, Benson, pl. I, fig. 17,18, 19. There are specimens of this shell amongst my Irawaddy collections: I think they are from Rangoon. The species is generally found in fresh or slightly brackish water, while Neritina crepidularia and N. cornucopia are chiefly met with nearer the sea, where the water is more salt. In Bombay Island, however, I have met with N. depressa on the sea shore.

No., 19, Neritina (Dostia) crepidularia, Less. Pl. I. fig. 20, 21, 22.

This shell and the next are found rather abundantly upon trees growing in places covered by water at each tide, and especially upon Nipa palms. N. crepidularia frequently occurs upon the sea shore, as well as in estuaries.

No. 20, Neritina (Dostia) cornucopia, Benson, pl. I. fig. 23, 24, 25.

Locally abundant. The shells found by me in Pegu differ slightly from the type, which is scarce in the Hoogly at Calcutta. In the latter, the apex of the shell is very nearly in the same plane as the edge of the peristome, sometimes actually so and touching it. In Pegu specimens, the peristome is free from the apex. The difference is very trifling, and there is slight variation in this character in specimens from the same river. In other respects, the shells appear to agree excellently.

I learned from Mr. Benson some years since that Neritina melanostoma, Troschel, is identical with N. cornucopia, the latter name having priority.† The figures of the former in Philippi's Abbildungen

*Further examination shews it to be one of the forms already referred to as intermediate between N. Peguensis and N. retifera, B. It is smooth like the latter.

+ N. melanostoma was published in Wiegman's Archiv for 1837, p. 179; N. cornucopia was described by Mr. Benson in this Journal for 1836. Vol. V. p. 748.