NORTH AMERICAN FRESH-WATER LEECHES. 673 



nished with six longitudinal plications. Ocelli, ten : the fourth pair on 

 the buccal segment; the fifth on the second segment behind the buccal. 

 Anus dorsal, at the posterior end of the body. Acetabulum round, 

 separated from the body by a deep constriction. 



This genus, although evidently allied to Seniiscolex, differs in the 

 structure of the cephalic lobe and oesophagus. 



Hexabdella depressa Verrill. 



Op. cit., vol. iii, p. 1:^6, 1872. 



Body strongly annulated, broad and much flattened posterior to the 

 clitellus, tapering and somewhat rounded in front of it. Length, in partial 

 contraction, 1.50 inches; breadth 0.40 inch. Head, or cephalic lobe, 

 somewhat elongated, rounded in front, with four annulations, the first 

 or terminal one oval, separated from the following by a decided depres- 

 sion, or fossa. Ocelli, ten: the first pair near together on the posterior 

 edge of the first cephalic segment; the second pair, on the second, and 

 the third, on the third segment, form a nearly regularly curved line; 

 those of the fourth pair are on the sides of the fifth or buccal, segment ; 

 and those of the fifth are on the seventh segment, or the third of the 

 body. Cephalic lobe divided beneath into three broad lobes by two deep 

 sulcations,eaclj lobe subdivided into smaller ones by less marked, diverg- 

 ent grooves. Behind each of the three lobes, there is an elevated, trans- 

 verse, rounded, fleshy lobe, or fold; behind these, and separated by a 

 deep groove, there are six well marked plications in the oesophagus. 

 Anus with elevated, crenulate borders, Male organ between the twenty- 

 fourth aud twenty-fifth segments of the body. Acetabuluin round, of 

 moderate size. Colorof the preserved specimen, dark slate-brown above, 

 with few irregularly scattered, remote black spots, and with still fewer 

 small, white specks ; beneath, lighter slate-brown, with very few black, 

 sxjots toward the margins. 



Near New Haven, Connecticut — A. E. Yerrill. 



Nephelopsis Yerrill. 



American Journal of Science, vol. iii, p. 135, 1872. 



Body broad and flattened behind the clitellus, rounded and tapering in 

 front of it. Upper lip large, dilated, wrinkled, and radiately sulcated 

 beneath; cesophagus with three broad folds, as in N'ejjhelis. Intestine 

 simple, resembling that of Trocheta. Ocelli eight, in the typical species. 

 External male organ expanded at the end into a disk-like form, with a 

 raised margin and depressed center, in which there is a four-lobed ori- 

 fice, as in Trocheta. The internal male organs resemble those of Aulas- 

 tomum and Hirudo; the testicles being rather large, rounded or pyriform 

 vesicles, apparently but eleven on each side. 



This genus has a remarkable combination of the characters of Nephe- 

 lis, Trocheta, and Aulastomum. In general habit and form of body, it is 

 much like Trocheta, but there are no maxillne. 

 S. Mis. 71—43 



