1894.] NATURAL SOIKNCES OF PHILADELPHIA. 449 



PTERODRILTJS, A REMARKABLE DISCODRILID. 

 BY J. PERCY MOORE. 



Among a number of additional new species of Discodrilidse, which 

 have come into the writer's possession, are two which differ so remark- 

 ably from the known type of structure of these interesting parasites 

 that an immediate description of their peculiarities seems desirable. 

 A new genus, Pterodrilus, is proposed for them, characterized by the 

 presence on certain of the post-cephalic somites of paired dorsal aj)- 

 pendages, chiefly developed from the muscular layers of the body 

 walls. The genus resembles American Discodrilids hitherto de- 

 scribed in the presence of a second pair of vasse deferentiaj in the Vlth 

 post-cephalic somite, in addition to the pair in the Vth somite, which 

 alone is present in the Eui'opean Branchiobdella. Both pairs open to 

 the exterior in the Vlth somite by the usual form of efferent apparatus. 

 The dorsal and ventral cuticular jaws are similar to one another, and 

 each is normally bi-laterally symmetrical, though not infrequent varia- 

 tions affecting this symmetry are notable. The external openings of 

 the anterior pair of nephridia are united in a common muscular vesicle 

 having an outlet on the dorsum of somite III. 



In the two species at present known the spermatheca is a simple 

 sac with glandular and muscular walls, opening on the ventral 

 middle line of the Vth somite. The atrium shows the usual division 

 into bursa, penis sheath, and glandular atrium, the vasa deferentia 

 opening into the latter, which is short and stout. The ovaries are 

 attached to the posterior face of the septum VI-VII, and the 

 ovipores are situated between the major and minor annuli of 

 somite VII. 



As usual in the Discodrilidie the nervous system consists of a 

 doubly bi-lobulate supra-oesophageal ganglion, united by partly gang- 

 lionic ci renin- oesophageal connectives with the ventral nerve cord, 

 which develops three pairs of deeply bilobed cephalic ganglia, eight 

 pairs of double post-cephalic ganglia, and a posterior nerve mass 

 composed of three fused pairs of double ganglia, making a total of 

 eleven post-cephalic ganglia, corresponding to the eleven bi-annulate 

 body somites. 

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