NORTH AMERICAN FRESH-WATER LEECHES. 667 



b b. Ocelli in one to four pairs along the median 



line; an exsertile proboscis Clepsine, (p. G77.) 



bbb. Ocelli none ; no proboscis Liostomum, (p. G88.) 



c. QSsopliagus with folds, and armed with three 



convergent jaws, {d:) 

 cc. Oesophagus with folds; no jaws, (/:) 



d. Jaws with denticles, {e :) 



d d. Jaws without denticles Democedes, (p. 671.) 



e. CEsophagus with 9 folds ; jaws iwomment.. Macrobdella, (p. G67.) 

 ee. Qi^sophagus with 12 folds; jaws small Aidastomum^ (p. 670.) 



eee. CEsophagus with 6 folds; jaws broad Hlrudo, (p. 688.) 



/. Folds, 12; 3 transverse lobes ; ocelli, 8 or 10 . Semiscolex, (p. 671.) 



//. Folds, 6; 3 transverse lobes; ocelli, 10 Hexabdella, (p. 672.) 



fff. Folds, 3 ; no transverse lobes ; ocelli, 6 or 8, 



g. Body distinctly dilated and flat posteriorly; 



ocelli, 8 Nephelo2)sis, (p. 673.) 



gg. Body not much dilated posteriorly ; sub-de- 

 pressed ; ocelli, 6 or 8 Nephelis, (p. 675.) 



h. Body subterete ; no lateral appendages, (i:) 

 h h. Body somewhat depressed ; a row of pulsat- 

 ing vesicles along each .side Cystobranckus, (p. 685.) 



i. Head obliquely attached, dilated ; margins 



not fringed Ichthyobdella, (p. 686.) 



i i. Head campanulate ; margin fringed with mi- 

 nute bristles Astacobdella, (p. 688.) 



Macrobdella Verrill. 



American Journal of Science, vol. iii, p. 137, 1872. 

 Body strongly annulated, stout, broad, depressed throughout, taper- 

 ing but little. Cephalic lobe large, rounded in front, composed of five 

 segments, its lower surface rugose with longitudinal sulcatious, and at 

 the base having a transverse fold, which forms sockets for the protec- 

 tion of the maxillae when retracted. Maxillae three, stout, and promi- 

 nent, the outer edge denticulate, with numerous acute teeth. Nine pli- 

 cations within the cesophagus. Stomach voluminous, divided into 

 several compartments, with very large and irregular dilations or pouches 

 on each side. Ocelli 10. Male orifice of the typical species in the 

 twenty-seventh* segment behind the mouth ; vulva between the thirty- 

 first and thirty-second. Anal opening dorsal, in advance of the pos- 

 terior sucker. 



This genus has a remarkable combination of the characters of several 

 diverse genera. It has, like Bdella, sulcatious on the cephalic lobe 

 beneath; maxillae similar to those of Hiriido, but more prominent; a 

 plicated oesophagus, similar to that of Aulastomum ; a stomach most 



* Leidy says that the male orifice perforates the twenty-fifth annulus, but he appa- 

 rently excludes the buccal segment from his count. 



