1894.] naturaIj sciences of Philadelphia. 453 



Its lower half is narrow and cn^lindrical, its upper abruptly ex- 

 panded. 



The copulatory bursa is rather thin walled, and with the penis is 

 capable of complete invagination. The penis sheath is relatively 

 short, and exhibits no muscular atrial enlargement at the upper end. 

 The glandular atrium is short, nearly spherical, and thick walled. 

 It receives the vasse deferentire, which are of the usual form. In the 

 mounted specimen, from which figure 1 was drawn, the atrium was 

 twisted so that in the figure the anterior end is directed posteriorly. 



The common opening of the anterior pair of nephridia is located on 

 the doi-sum of the major annulus of somite III, immediately pos- 

 terior to the dorsal appendage. 



The largest examples found among about a dozen specimens 

 measure about 1 mm. in length. 



This species was found on Cambarus aeuminatus, in the Johns 

 River, Watauga Co., N. C. , in the summer of 1893; but what part 

 of the crayfish it inhabits was not determined, nor have cocoons 

 been found. 



Pterodrilus distichus sp. nov. 



PI. XIII, fig. 2, profile of entire animal, showing intestine, sper- 

 matheca, atrium, ovary and ovipore of one side, etc. X 145. 



Fig. 2a, a jaw. X (340. 



Fig. 2h, transverse section through the Vlllth somite, showing 

 the dorsal appendages, and the thickening of the body wall, with the 

 intestine, nerve cord, and portion of a nephridium. X 145. 



Fig. 2c, the male efferent apparatus, figured from a dissection ; «, 

 glandular atrium; b, copulatory bursa; c, penis sheath; d, bursal 

 glands. X about 200. 



Fig. 2d, section across the glandular atrium. X 500. 



In form this species is similar to P. alcicornus, but the head is 

 rather more robust, and the Vllth somite is of greater diameter than 

 VI or VIII. 



Dorsal appendages are present on post- cephalic somites II to VIII 

 inclusive, and are much simpler than in P. alcicornus. The dorsal 

 ridges are not compressed and plate-like, and are similar on all the 

 somites. On somites II to VII each bears a pair of bluntly pointed 

 cylindrical lateral appendages, while somite VIII bears two pairs; 

 they become somewhat larger anteriorly. 



These appendages contain no longitudinal muscle fibres, and the 



