HIRUDINEA AND OLIGOCHiETA OF THE GREAT LAKES KEGION. 



KjI 



of the type. ^lach is yet lacking in our linowledge of the organization of these interesting leeches, l)ut 

 it is hoped that a complete account of their anatomy can soon be published. At the present lime it 

 seems evident that AcUnobdella approaches Placobdella most closely, especially in the character of the 

 reproductive organs, gastric cseca, and sense organs, while it differs from that genus and resembles 

 Ghssiphonia in the possession of diffuse instead of compact salivary glands. The fact that certain 

 species of Placobdella, notably P. phalcnt and P. montifera, possess small marginal papillje on the caudal 

 sucker is a further indication of relationship which may eventually necessitate a generic grouping 

 somewhat different from that here adopted. 



A. anneclens, like A. inequiannulata, is a small blood-sucking glossiphonid, the type of which is 

 9 mm. long, 2 mm. wide, and about 1 mm. high. The general form is nmch like that of Glossiphoimi 

 fusca but considerably more slender; the body is strongly convex above, flat below, the region of the 

 gastric caca about half round; the head end, with the sucker and mouth, have the typical glossi- 

 phonid form; and the thick, prominent, hemispherical caudal sucker measures 1.2 mm. in diameter 



and its pedicle is contracted and centrally attached, indicating great mobility in this region. Tlie 

 marginal papillse of the caudal sucker form a ready means of distinction between this species and 

 .1. iDcijukinnulata, for whereas the latter possesses about thirty very prominent papilla?, .1. anneclens 

 has about sixty much smaller ones. They are unfortunately much contracted, but are clearly con- 

 tinuations of radiating ridges on the ventral surface of the sucker and have the same structure and 

 relation to compact aggregated glands as in the type species. These glands form a conspicuous ring a 

 short di.stance from the margin of the sucker, the dorsal surface of which they elevate into a circular 

 ridge. In correspondence with the smaller and more numerous papillje these glands differ from those 

 of A. inequiannulata, and at places the continuity of the ring is interrupted by the absence of several 

 together. 



A single pair of very large and conspicuous eyes are situated on somite III, with their pigment 

 cups in contact and united in the middle line and reaching into IV. Immediately behind the eyes is 

 a large aggregation of reserve cells extending over the middle portion of somites IV and V and 

 margined by pigment cells. A similar patch occurs on annuli VI a3 and VII al, and others are 



