New Species Branchiobdellid 27 



diameter than the anterior one, conferring a generally smooth appearance 

 to the outline of the body. 



There is a pronounced external sulcus or constriction of the head im- 

 mediately posterior to the position of the jaws. No other external evidence 

 of the segmentation of the head is apparent. Both upper and lower lips 

 bear very shallow and narrow emarginations. Oral papillae are not detec- 

 table in our specimens. There is one internal pharyngeal sulcus, deep, and 

 closely compressed, delimiting the posterior 1/3 of the head region from 

 the anterior 2/3. 



The jaws are subequal in size, their width about 1/8 the greatest 

 diameter of the head. They consist of subquadrangular plates carrying 

 prominent teeth-bearing ridges. The dental formula is 4/4 and the lateral 

 teeth are longer than the median ones and often noticeably diverge 

 laterad. The teeth may be blunted, particularly the median ones, 

 presumably by wear. The jaws are brown; the teeth colorless. 



The sperm funnels are narrow; not conspicuously set off from the vasa 

 efferentia by constrictions. The vasa deferentia are short and thick, enter- 

 ing the ental borders of the spermiducal gland at widely separated por- 

 tions of its ventral surface. 



The spermiducal gland is short and thick and roughly subspherical. Its 

 ventral (ental) border lies just dorsal and to the side of the bursa; its dorsal 

 border extends to about the mid-portion of its segment. Its most dis- 

 tinctive feature, aside from shape, is the capaciousness of its lumen 

 (obscure in most branchiobdellids) which is expanded so that it appears 

 as a thin-walled sac filled with a clear fluid. Moreover, again unusual, 

 there are small amounts of spermatozoa clustered in the central portion. 

 The wall of the spermiducal gland is, however, composed of the usual ele- 

 ments (Holt 1949) of a peritoneal investiture, a thin muscular covering 

 and a lining of glandular epithelium. 



The ejaculatory duct is a long and prominent tube composed of the 

 usual layers of muscle. The bursa is small and subspherical, in diameter 

 about 3/4 that of the segment (VI) in which it lies. There is a short ectal 

 (outlet), narrowed portion and the penis is a simple, protrusible, muscular 

 cone, exserted, one presumes, by the eversion of the bursa. 



The spermatheca has a relatively long ectal duct and the cylindrical 

 bulb bends dorsad between the gut and the body wall. The curvature of 

 the organ precludes, in the absence of tedious and essentially impossible 

 procedures, any just estimate of its length. 



Variation: — Beyond the usual differences in size and those produced by 

 differing degrees of contraction at death, there are few variations of note. 

 The relative lengths of the teeth seem to differ, but the lateral teeth are 



