No. I.] SPHYRANURA OSLERF. ^ 



edge of the anatomy of the monogenetic Trematodes renders 

 possible a better representation of their phyletic relationship) 

 Sphyranura ought to be associated with Polystomum under the 

 sub-family Polystomidae, as it is clearly more closely related to 

 that genus than are the Selachian ectoparasites Onchocotyle 

 and Erpocotyle, or the Diplobothrium of the Sturgeon, which 

 three genera, on the other hand, form a very natural group. It 

 is interesting to note that, leaving Aspidogaster out of the 

 question, the five genera constituting this sub-family are the 

 only monogenetic Trematodes which do not occur on Teleosts. 

 The following slight alteration of the diagnosis, furnished by 

 Taschenberg, is necessary to admit of the genus Sphyranura: — 



Sub-family Polystomidce. 

 Without accessory anterior suckers, caudal lamina armed with two strong 

 hooks often carried on a special appendage. Suckers, sometimes two, gener- 

 ally six, in two parallel rows on the ventral surface of the caudal lamina. 

 Sexual apertures in the ventral middle line. Two vaginae opening on the 

 right and left borders, or absent (or a single one opening ventrally? '). Egg- 

 shells with or without polar threads. 



Access to fresh specimens has rendered possible some emen- 

 dation of the diagnosis previously furnished for Sphyranura. 



(Fain. Polystomecs, Taschenberg.) 



Sphyranura, char, emend. 



Caudal lamina, considerably wider than the slender body, with two immersed 



suckers, two large hooks behind these, and sixteen small hooks (seven along 



each side of the lamina, and one in each sucker). Two contractile bladders 



anteriorly, each with a dorsal excretory pore. No lateral vaginje. Oviparous. 



S. Osleri. 

 Body 2.6-4 i""™- in length, 0.7 mm. in breadth, narrowed at each end, 

 especially where it joins the caudal lamina, which is 1.2 mm. broad, and about 

 0.6 long. Large hooks, 0.24 mm. long. Lobules of testis, 12-16 in number, 

 occupying the interval between the intestinal coeca, which anastomose poste- 

 riorly. Uterus with single mature egg, oval, with brownish-yellow shell, 

 0.4 X 0-2 mm. 



Since the publication of the original description no favorable 

 opportunity occurred to verify it till the spring of the present 



* We share the doubt expressed by Ijima, that the tube in Onchocotyle, here re- 

 ferred to, is a vagina. Z06I. Anz., vii., 638. 



