' NORTH AMERICAN FRESH-WATER LEECHES. G67 



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



line; an exsertile proboscis Clepsine, (p. 677.) 



hhb. Ocelli none ; no proboscis Liostomum, (p. 088.) 



c. CEsopliagus 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. CEsophagns with 9 folds ; jaws pvomineut. .MacrobdeUa, (p. 607.) 

 €€. Q^sophagus with 12 folds; jaws small Aulasto7num, (p. 070.) 



eee. O^sophagns with 6 folds; jaws broad nirudo, (p. 688.) 



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



//. Folds, 0; 3 transverse lobes; ocelli, 10 Hexabdella, (p. 072.) 



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



g. Body distinctly dilated and flat posteriorly; 



ocelli, 8 Neplielopsis^ (p. 073.) 



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

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



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

 hh. Body somewhat depressed ; a row of pulsat- 

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



i. Head obliquely attached, dilated ; margins 



not fringed Ichthyobdella, (p. 080.) 



i i. Head campannlate ; margin fringed with mi- 

 nute bristles Astacobdella, (p. 088.) 



Macrobdella Verrill. 



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



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

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

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

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

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

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

 cations within the oesophagus. 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, sulcations on the cephalic lobe 

 beneath; maxillas similar to those of JT/Vw/o, but more prominent; a 

 plicated oesophagus, similar to that oH Aiilasto mum ; a stomach most 



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

 rently excludes the buccal segment from his count. 



