to be hitherto undescribed. All the Leeches were found in comparatively shallow water, none being detected in depths greater than three fathoms. They all belong also to small forms of Clepsine and Nephelis; but an examination of the shallower parts of the lake in early spring would doubtless bring to light some forms of greater size.

1. Clepsine patelliformis, Nich.

Body much depressed, convex above, flattened or slightly concave below, the width nearly as great as the length when the animal is contracted. The adult is ovate in shape, the anterior extremity somewhat acuminate and narrower than the posterior. The length varies from one-fifth to one-half of an inch; the greatest breadth being about one-fifth of an inch. On the under surface of the head is placed the mouth, in the form of an oval aperture about onetwentieth of an inch in breadth.

The colour is sometimes dark greenish-brown, sometimes nearly black, sometimes light-brown; always covered with innumerable minute black points and numerous yellow spots, the latter being especially abundant towards the margins. The colour probably varies with that of the object to which the leech adheres; but this point was not specially observed. In all the lighter-coloured specimens there are two very distinct dorsal black lines, somewhat interrupted, and placed one on each side of the median line of the back (Fig. 1). In the darkest specimens these lines are hardly distinguishable. In all

FIG. 1. Clepsine patelliformis, Nich.-a. Dorsal view of the adult, considerably enlarged. b. Ventral surface of the adult, showing the posterior sucker and the parasitic young.

specimens, however, the ventral surface is lighter than the dorsal, and exhibits two distinct black lines, also somewhat interrupted, and also placed one on each side of the middle line of the body. Both the dorsal and ventral lines are slightly curved, and approach one another toward the two ends of the body. Just at the commencement of the dorsal lines, on the top of the head, are situated six minute black ocelli, arranged in three closely approximated pairs one behind the other, the two posterior pairs being the largest and most conspicuous (Fig. 2, b).

FIG. 2.-Clepsine patelliformis, Nich.—a. Outline of adult viewed from below, showing the mouth, ventral lines, and acetabulum. b. Anterior extremity, enlarged to show the ocelli. c. Young, much enlarged, to show the sacculated stomach and pedunculate sucker. The straight lines indicate the real sizes of the adult and young.

The habits of this little leech are very remarkable. The adult leech usually places itself with its ventral surface closely appressed to some foreign body, such as a stone or a dead shell, to which it adheres firmly, like a limpet or small Chiton. It is from this habit that the specific name of patelliformis has been chosen. When forcibly detached or irritated, it rolls up like a hedgehog or like the Myriapods of the genus Glomeris. The object served by these peculiar habits becomes obvious when it is seen that almost every individual carries attached to the ventral surface of the body a large number (from twenty to thirty) of young leeches (Fig. 1, b).

The young are attached to the ventral surface of the parent posteriorly in a close cluster, which is surrounded on all sides by a vacant space. Each adheres to the adult by means of the posterior sucker, which is very distinctly marked and constricted off from the rest of the body (Fig. 2, c.) The length of the young varies from about to of an inch; the color being light yellow or reddish, and the

body being semi-transparent. The gullet is distinct, and leads into a much sacculated stomach, which is very conspicuous from its dark color (Fig. 2, c). The annulations of the body are very distinct, and the integument is finely tuberculated or papillose.

This extraordinary habit of carrying the young has been noticed by Prof. Verrill, in another species of Clepsine (Amer. Journ. Science and Arts, III., Feb., 1872); but I am not aware that attention has otherwise been drawn to it.

In my "Preliminary Report," (Annals of Natural History, Oct., 1872,) I referred this species to the genus Nephelis, but it is more satisfactorily placed under Clepsine.

Hab.-Common in from two to three fathoms, adhering to stones or to the shells of Unio crassidens.

2. Clepsine sub-modesta, Nich.

Length in contraction, one-fifth of an inch; in extension, one-quarter to one-half of an inch. Body a long oval, attenuated in front when extended, convex above, concave or flattened below. Back smooth. Two minute black ocelli carried upon the top of the head. The margins of the body exhibiting broad transparent papillose margins, the rest of the body being of a light, dirty, greenish-brown colour. (The preserved specimens are nearly white.) Behind the head, in the middle line of the back, is placed an auditory vesicle or "cervical gland," in the form of a rounded, slightly prominent, chestnut brown spot. Sometimes there are two of these, the smaller being placed a little behind the other (Fig. 3).

The habits of this species are very similar to those of C. patelliformis. It carries its young attached to the posterior portion of the ventral surface in a bunch or cluster, and it rolls up into a ball when irritated. The attached young are about a line in length, of a pale whitish-brown colour, semi-transparent, and showing the brown line of the alimentary canal.

FIG. 3.-Clepsine sub-modesta, Nich.-a. Outline of adult viewed from above enlarged. b. Side view of adult, enlarged, showing the attached young.

This species is nearly allied to Clepsine modesta, Verrill (Amer. Journ. Science and Arts, III.. Feb., 1872); but it is distinguished

by its much smaller size and paler colour, as well as by the broader and less attenuated form of its anterior extremity. On the other hand, C. modesta is described as reaching the length of an inch and a half in extension, being "pale purplish brown or purplish flesh-colour, with minute specks of brown, and very small round spots of a dull yellow, and often of a light green." The anterior portion of the body also is very slender and attenuated. Much stress can not, perhaps,

be laid upon the differences in color, but the other distinctions appear to have a specific value.

Hab.--Common in from one to three fathoms, mostly adhering to aquatic plants, but also found on pebbles or dead shells.

3. Nephelis lateralis, Say, sp. (?)

The original specimens on which this species was founded were originally obtained by Say from the waters between Rainy Lake and Lake Superior, and were named by him Hirudo lateralis (Long's Second Expedition, Vol. II., p. 267, 1824.) They were subsequently referred to the genus Nephelis, by Prof. Verrill (Amer. Journ. Science and Arts, II., p. 451). Say described the species as being of a livid colour, with a rufous line along each side and a few very remote minute black points, the ocelli being six in number, and placed in a regularly curved line.

The specimen which was obtained in Lake Ontario, and which I have doubtfully regarded as a young example of this species, was about an inch in length when at rest. The colour in life was a liverbrown, not exhibiting any lateral lines. In the specimen preserved in spirits the ocelli can not be made out. Our example, however, agrees with those described by Verrill in being slender and somewhat rounded in front, with rounded lateral margins, and having the posterior portion of the body somewhat depressed.

Hab. A single specimen was dredged in Toronto Bay in a depth of three fathoms.

4. Nephelis vermiformis, Nich.

A small worm-like leech of a red colour during life. Length about half an inch in contraction and one inch in extension; the greatest width about one line. The body slightly narrower anteriorly than posteriorly. Acetabulum oval, oblique, as wide as the body.

Mouth small and rounded, the lips with several folds. In the speci mens preserved in spirits no ocelli could be made out.

Though

FIG. 4.-Nephelis vermiformis, Nich. Enlarged.- -a. Acetabulum.

certainly new to America, it is possible that this form is only a variety of some other species, but the impossibility of obtaining access to the necessary works of reference renders me unable to speak positively on this point.

The habits of Nephelis vermiformis are very different from those of the two species of Clepsine already described. Instead of remaining quiescent, attached to some foreign body, it is exceedingly active in its movements, swimming gracefully through the water by means of a serpentine bending of the body.

Hab.-Rare in three fathoms, Toronto Bay.

5. Sænuris Canadensis, Nich.

A very slender worm, averaging about an inch in length, but sometimes a little longer or shorter. The body tapering and attenuated posteriorly; the width behind the head being about one twentyfifth of an inch. Intestine moniliform; anus terminal, with three lobes. Setæ in four fascicles on each segment; each fascicle of three or four setæ; the setæ forked and hooked at their tips. Colour during life red.

Owing to some defect in the spirit in which these specimens were originally put up, their state of preservation was so bad as to render it impossible to make out many important points in their organisation. I have, however, no doubt as to the specific distinctness of this form. It is most nearly allied to the Sanuris limicola of Verrill, obtained in Lake Superior, but it is much larger, and the setæ are hooked and bifurcate at their tips, instead of being simply curved and acute.

Hab.-Extraordinarily abundant at all depths in Lake Ontario, wherever the bottom consisted of a fine argillaceous mud. Beyond