494 



FAUNA CANADENSIS. 



to be liitlierto imdescribed. All the Leeclies were found in compara- 

 tively shallow water, none being detected in depths greater than 

 three fathoms. They all belong also to small forms of Clepsine and 

 Nephdis ; but an examination of the shallower parts of the lake iii 

 early spring would doubtless bring to light some forms of greater 



size. 



1. Clepsine fatelliformis^ 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 i'3 ovate in shape, the antei-ior 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 siu-face of the head 

 is placed the mouth, in the form of an oval aperture about one- 

 twentieth 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-coloiired 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 



^u. -1 



Fig. I. Clepsine patclUformis,'H\<^\. — a. Dorsal view of the adult, considei-ably 

 enlarged, b. Ventral surface of the adult, showing the posterior sucker and the 

 parasitic young. 



