332 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



unpaired excretory vesicle forks to form two crura which reach to the 

 anterior end of the disc. 



The name pacificum indicates that this is the first species of the genus 

 known from the Pacific Ocean. 



Comparisons. L. pacificum differs from L. ringens in number of 

 loculi on the disc (the various descriptions of L. ringens give the mar- 

 ginal loculi as 36 to 42 and the transverse loculi as 16 to 18 in number) ; 

 in a longer portion of the body posterior to the disc, and in that the eggs 

 do not become so large (eggs are commonly 80 /a long in L. ringens, and 

 one record gives 103 by 58 ju,). 



L. pacificum is more similar to L. kemostoma, agreeing in number of 

 loculi, in egg size, and in long hindbody. On the basis of the figures and 

 descriptions given for L. kemostoma, L. pacificum seems to differ in the 

 following respects : ( 1 ) the dorsal median lip is smaller than the others ; 

 (2) the disc is relatively longer, at least about ^^ total body length and 

 usually over ^ (in L. kemostoma it is about Yz body length) ; (3) the 

 ovary and almost always the testis are dorsal to the disc rather than 

 posterior to it; (4) the vitellaria extend from near the anterior end of 

 the disc to the end of the cecum rather than from behind the middle of 

 the disc to near the posterior end of the body. 



A 1.417 mm specimen of L. pacificum was immature and a 1.830 mm 

 specimen contained but one egg. 



All three species of Lobatostoma are found in Trachinotus species, 

 although L. ringens also occurs in a variety of other fishes. 



Discussion. The muscular septum separating a dorsal portion of 

 the body from the ventral disc is verj^ conspicuous especially in young 

 specimens. The dorsal portion contains the intestinal cecum, the vitel- 

 laria, and some of the uterus; but most of the reproductive organs and 

 also the excretory crura lie in the ventral portion. The septum has the 

 same musculature as the body wall, and it seems evident that it repre- 

 sents the body wall of the posterior portion of the larva as the posterior 

 sucker advanced forward to form the ventral disc. 



GASTEROSTOMATA Odhner, 1905 

 Bucephalidae Poche, 1907 



Odhner (1905), recognizing the important differences between gas- 

 terostomes and other digenetic trematodes, established the suborders Gas- 

 terostomata and Prosostomata. He studied Prosorhynchus squamatus in 



