AET. 22 TWO SPECIES OF TREMATODE WORMS PRICE 5 



situated in the posterior end of the body and are unequal in size. 

 The anterior testis is rounded, 248/^ by 217/x; the posterior testis is 

 about 200/x in diameter and lies somewhat postero-dorsal of the ante- 

 rior. Ovary round to oval, 125^ to 155jii in diameter, pretesticular, 

 and situated to the right of the median line. The shell gland is 

 about one-half the size of the ovary and is situated somewhat dorsal 

 to it. The uterus runs anteriorly in irregular transverse coils and 

 terminates in a metraterm which is about one-half the length of 

 the cirrus pouch. The vitellaria are extracecal and composed of 

 large, discrete, rounded follicles extending from the level of the 

 posterior edge of the ovary to the level of the origin of the metra- 

 term. Eggs oval, 23ju long by VSjx wide, provided with a long filament 

 at each pole. 



Hosts. — Amyda ferox and A. spiniferar 



Location. — Oviducts and intestine. 



Distribution. — United States (New York, N. Y., and Woods Hole, 

 Mass.). 



From the above description the genus may be tentatively defined 

 as follows: 



Genus OPISTHOPORUS Fukui, 1929 



Generic diagnosis. — Pronocephalidae : Body spindlelike in outline, 

 more attenuated posteriorly than anteriorly ; cuticle smooth and with- 

 out spines ; cephalic collar present. Oral sucker subterminal ; esopha- 

 gus simple; intestinal ceca without lateral diverticula. Genital pore 

 median; cirrus pouch pestle-shaped, well developed; cirrus spiny; 

 testes situated in posterior end of body with their fields coinciding 

 and zones slightly overlapping, the posterior testis being slightly 

 dorsal of anterior ; ovary pretesticular, to right of median line ; shell 

 gland dorsal and slightly median of ovary; vitellaria extracecal, ex- 

 tending from ovary to level of origin of metraterm; egg with long 

 filament at each pole. Parasitic in turtles. 



Type species. — Opisthoporus aspidonectes (MacCallum, 1917) 

 Fukui, 1929. 



The genus Opisthoporus shows affinities with both the Notocotylidae 

 and Pronocephalidae, but its resemblances to the latter group are 

 greater than to the former. The position of the genital pore is sug- 

 gestive of the Notocotylidae, but the presence of a cephalic collar and 

 the pretesticular, dextral position of the ovary are characteristic of 

 most members of the Pronocephalidae; Opisthoporus is therefore 

 regarded as belonging to the latter family. 



Up to the present time the following genera have been included in 

 the family Pronocephalidae: Pronocephalus Looss, 1899; Charaxi- 



2 The writer is indebted to Miss Doris M. Cochran, of the U. S. National Museum, for 

 the correct names of these hosts. 



