from a small base, similar in size, obscurely heptagonal; at the terminations of the diameter opposite from the one which makes the suture line they are prolonged into quite acute angles, forming the two obscure angles of the heptagon. Immediately above the columnar pit, or a very little below it, is a series of massive tubercles irregularly disposed, and varying in size, the remainder of the bases being comparatively smooth. From the margin of the columnar pit extend, in the direction of the arms, four raised folds, two on each piece, ornamented by several tubercles and striæ.

Radials. The first are very large, pentagonal, trapezoidal in shape, their upper facets being much wider than the lower ones. They extend out as far as the first or second pieces beyond the axillary radials; the middle portions are swollen out into folds or plaits; their junction with the second radials is distinguished by a large tuberous knob, beneath which are one or two smaller ones. A number of striæ regularly disposed, and a few minute granules are scattered over the surface of the pieces. This raised median line of the radial pieces produces broad intervalla between each two of them. The second and third radial pieces are very minute; the second join the first radials at the knobby prominence described above; the third are axillary, and give off two rays each.

Inter-radials. One large inter-radial is placed between each pair of arms.

Anal piece. At one termination of the articulating facet of the basal piece (the other being at the anterior radial piece) is situated a single anal piece. It is not so wide as the radials, but of the same length, pentagonal; as in the radials, its centre is elevated, it differs from them in the portion where the second radials join the first; on the radials there is a well-defined, articulating facet, whilst on the anal piece none exists, the piece being solid and continuous throughout.

Vault. We have no specimen showing the vault; in one example before us, there is a proboscis much crushed and misshapen; it is large, composed of many small, coarse, tubercular pieces, and extends not quite one third the length of the arms. Its terminal point is apparently formed by two circles of pieces surrounding a single one. Arms. From each third radial come off two arms. They are about three times as long as the body, and arranged as follows: in each arm six quite stout quadrangular pieces, rounded on the dorsal surface, are superimposed upon each other; the sixth are axillary,

each give off two slender fingers, which are composed of the following pieces: first, one or two quadrangular ones, upon them from five to seven somewhat smaller wedge-formed ones placed one above another, the large end of one wedge being placed over the small end of the next, the wedges becoming gradually more acute, until on the sixth or seventh piece there commences a double row of small, quite acute, pentangular pieces, which alternate with each other, the salient edges of one row fitting into the retreating angles of the other row, the points of their junction being lateral, not central, as in most other genera having similar arms. Yet two more fingers exist on each arm; they are situated on the outer surfaces of the six pieces described above (the first one on the second piece from the last radial, the second one on the fourth piece from the same radial), the inner surfaces having no branches, and lying close together throughout their whole extension. They spring apparently from the sides of the pieces, the facets being on the sides, rather than on the top as in a regular axillary piece; curving out gracefully for a short distance, they continue in a straight line to their ends without any further bifurcation. They are slender, composed of pieces exactly similar to those of the fingers already described. On either side of the ambulacral grooves of the fingers is a row of stout pinnulæ.

.60

66

Length of proboscis (variable proportion in diff. sp.)

Geological Position and Locality. Rare in the silicious mud beds at the top of the Knob member of the subcarboniferous limestone, Hardin County, Kentucky; Montgomery County, Indiana, &c.

DICHOCRINUS SYMMETRICUS, Sp. Nov.

Body. The general form of the body is subconical; from the basis to the summit of the first radials it is basin-formed, above which it contracts upward and terminates in a point, formed by the large spinous piece which surmounts the vault.

The basal pieces, two in number, are of equal size, pentagonal; line of junction with each other straight, forming when united an irregu

larly-sided octagon. The columnar pit is shallow, oval; columnar facet obscurely pentagonal; perforation small and round. The pieces are prominent near the line marking their junction to those resting upon them, being suddenly reflected upward.

Radial pieces five, subquadrangular, the largest as wide as high, diminishing in size from the anterior piece on either side to the anal piece, swelling from the base and sides toward the superior margin, irregularly truncated above, slightly depressed at the summit between the pieces.

Second radials. Fragments of the second radials are attached to some of the first radial pieces; they are minute, and rise within the superior margin of the first radial pieces. The precise form of the second radials is not known.

Inter-radials. Between each group of arms, resting in the depression between the radials, is a single piece, usually pentagonal in form; it rises nearly as high as the opening into the body at the arms.

Anal pieces. Rising from the deepest angular notch at the junction of the basal pieces, is a large piece, the lower part of which is similar in form to the first radials, rising higher than they do; the upper margin is horizontally truncated about one third the breadth of the piece; the sides above the radials angularly sloping toward the top of the radials on either side; the centre of this piece supports one, and the sloping sides each support a piece of the second range of anal pieces; those on the sides correspond in size, form, and position, to the inter-radial pieces above described. These are again succeeded by a third range of pieces, triangular in form, three in number, the central one of which reaches the mouth (?), which is surrounded by three additional, small, long, narrow pieces. The series of pieces under the mouth are slightly depressed above the second range.

Summit. The summit above the radials recedes a considerable distance within the upper margin of the calyx. It is covered by numerous small polymorphous pieces, six of which are spinigerous; the largest and most prominent of these occupies the centre of the summit, immediately in contact with the pieces surrounding the mouth; the other pieces forming the second series of those rising above the openings into the body at the arms. The two spinous pieces above the arm-pieces of the postero-lateral rays form a circle around the central piece, the anterior part of the summit having one more range of pieces above the arms than above those arms on either side of

The Corresponding Secretary presented, from the authors, the following paper:

Description of two new Genera and eight new Species of Fossil Crinoidea, from the Rocks of Indiana and Kentucky. By S. A. CASSEDAY and S. S. LYON.

DICHOCRINUS, Münster.

In a résumé of this genus by MM. De Koninck and Le Hon, they state that, up to the appearance of their work,* only three species of this genus had been described; they add six, which, together with eleven described by American geologists, make in all twenty species. This comprises all the species of which we have any personal knowledge.

Heretofore much uncertainty has existed as regards the number and disposition of the radials and the arms. De Koninck and Le Hon give the following formula:

Basal pieces

Radial pieces.

Inter-radials

Anal piece

Arms.

Dr. B. F. Shumard, in some remarks about this genus, states as follows:-"The anatomical structure of a very perfect specimen of this genus corresponds only in part with the above formula. In our fossil we find a base of two pieces, supporting a circle of five large radials and one large anal piece, as in all known species of this genus. The radials however, are not repeated, but each one immediately gives rise to two brachial pieces, which are pentagonal, and in turn support, each, two simple arms; so that the number of the latter amounts to twenty."†

The Messrs. Austin, who up to this time have figured the most perfect examples of the genus, represent the number of radial pieces to be twenty, i. e. "five repeated four times."

"In D. ovatus there appear to be but ten, i. e. five repeated twice;

*Recherches sur les Crinoides.

Trans Acad. St. Louis, Vol. I. No. 1, p. 71.

while in D. cornigerus and D. sexlobatus, now described for the first time, the whole number of radials is only five."

In a number of well-preserved individuals of D. polydactylus, we have always found three radials, and on examination of other species we have concluded this to be the number most frequently met with. The following list contains all the species of Dichocrinus which show in a satisfactory manner all the radial pieces.

D. simplex also will doubtless show three radial pieces when perfect examples are found; D. cornigerus differs from other species in having two brachials coming immediately from the primary radial. This is the only species showing satisfactorily such an arrangement. Shumard quotes, above, D. ovatus as having two radials repeated five times, yet in his description of the species (Owen and Shumard, Geol. Survey of Iowa, &c., p. 590) he says, "Several joints of the arms remain attached to one of the superior plates, in the only specimen we have been able to procure. The first joint is of a rectangular form, and supports a cuneiform joint, on the bevelled edges of which is the commencement of the two series of smaller plates." The formula for the radial pieces will be,

Arms. But few specimens have been figured preserving the arms. They generally come off in five pairs, often bifurcating below, until they attain even to the number of forty divisions, as in D. polydactylus. D. fusiformis has ten arms (five pairs) without bifurcations. D. ovatus has, most probably, the same number. D. polydactylus, as we have

* Austin (Monograph of Crinoideæ, pl. 5, fig. 6, c) figures a single ray as having three small radials above the large primary radial. His specimen (pl. 5, fig. 6, b) is very imperfect, and we think it highly improbable that four radials exist in the individual there figured; such a mistake is more easily made than mistaking Dichocrinus elongatus for a Platycrinus. Hexacrinus macrostatus of the same authors has all the appearance of a Dichocrinus. (loc. cit., pl. 6, fig. 3, a.) J. Müller in his paper (Über neue Echinodermen des Eifeler Kalkes, pl. 1, fig. 3) figures a fossil which bears a most remarkable resemblance to a Dichocrinus; he calls it Hexacrinus.