8 PROCEEDINGS OF THE NATIONAL MUSEUM vol.78 



of Glyphicephalus as type, or (2), the name Pronocephalidae is invali- 

 dated by the designation of Glyphicephalus as type and a new family 

 name must be proposed. Pronocephalus^ unfortunately, is one of the 

 least typical of the genera of this group, but in view of the fact that 

 the adoption of the second alternative would introduce a new and 

 unfamiliar name for one which has been in use for almost 30 years 

 and would serve no useful purpose, it is the writer's opinion tliat the 

 family Pronocephalidae should be retained in spite of its atypical 

 type genus. 



The genera assigned to the family Pronocephalidae appear to fall 

 into three distinct groups which are regarded as constituting sub- 

 families and the following classification is, therefore, proposed with 

 keys as formulated here for the separation of the genera : 



Family PRONOCEPHALIDAE Looss, 1902 



Synonym. — Opisthoporidae Fukui, 1929. 



Family diag7iosis. — Elongated monostomes, more or less deeply 

 concave ventrally and convex dorsally; anterior end usually pro- 

 vided with a collarlike enlargement ; posterior end either rounded or 

 truncate, or provided with two papiilalike processes. Oral sucker 

 simple, terminal, or subterminal; intestinal ceca simple or provided 

 with diverticula, and extending to posterior end of body. Excretory 

 pore dorsal, near posterior end of body; excretor}^ vesicle Y-shaped, 

 the stem extending to the shell-gland complex and the limbs extend- 

 ing to the anterior end of body. Genital pore in the anterior half 

 of the body, usually to the left of the median line. Cirrus pouch 

 well developed, containing cirrus, ductus ejaculatorius, and pars 

 prostatica ; seminal vesicle convoluted and lying free in parenchyma ; 

 testes usually postovarial, entire or divided into follicles, zones coin- 

 ciding or overlapi^ing, and fields usually separate. Ovary pretesticu- 

 lar or posttesticular, to the right of median line; shell-gland complex 

 median, postovarial; Laurer's canal present; receptaculum seminis 

 absent ; vitellaria moderately developed, extracecal, in posterior half 

 of body ; uterus consisting of regular transverse coils terminating in 

 well-developed metraterm; eggs relatively small, numerous, usually 

 provided with polar filaments. Parasites of cold-blooded vertebrates. 



Type genus. — Pronocephalus Looss, 1899. 



KEY TO THE St'EFAMtLIES OF PROKOCEPHALIDAE 



1. Testes postovarial and tandem in position ; genital pore in median line. 



Opisthoporinae. 



Testes preovarial or postovarial, latei'al and opposite in position ; genital pore 



to left of median line 2. 



2. Testes preovarial Charaxicephalinae. 



Testes postovarial Pronocephalinae. 



