NO. 15 VAN CLEAVE : ACANTHOCEPH ALA 507 



the 2 dorsalmost rows, either the space immediately anterior to the hook 

 with the enlarged root is entirely devoid of hooks, or the hooks are repre- 

 sented by poorly formed vestiges for a space corresponding to the positions 

 of 4 hooks in adjacent longitudinal rows. The third row from the median 

 dorsal line of the proboscis on each lateral surface possesses a basal comb 

 containing 5 thorns, one less than in the 4 dorsal combs. In these third 

 rows from the middorsal surface, a single enlarged thorn occupies a 

 position comparable to the location of the heavily rooted hooks in the 

 dorsal series. A single thorn, slightly detached from the comb series, lies 

 between the comb and the hook standing on the same level as the hooks 

 with enlarged roots. In this same third row from the median dorsal 

 plane on the lateral surface of the proboscis, the location of the vestigial 

 hooks of the dorsal series is occupied by 2 very heavy hooks with heavy 

 roots, but the roots are approximately 40 /x long with the recurved hook 

 portion 27 [x long. The 6 ventral rows of hooks show very little regional 

 specialization. In these, the basal comb of 6 or 7 thorns is followed ante- 

 riorly by 2 very heavy, thornlike hooks, of which one serves as transition 

 to the form of the long, arcuate hooks characteristic of the anterior region 

 of the proboscis. Anterior to the various characteristic basal modifications, 

 the remaining hooks show little regional differentiation, except that hooks 

 on the ventral surface are somewhat heavier and more strongly recurved 

 than those on the corresponding region of the dorsal surface. The hyaline 

 cuticular membrane surrounding the proboscis is not so pronounced as in 

 Tegorhynchus brevis but surrounds each hook in a sheath much as in 

 the genus Leptorhynchoides. 



Lemnisci very thin and much coiled, apparently a little longer than 

 the length of the receptacle. 



Embryos within one gravid female 84 to 93 /a long by 21 to 24 ju. 

 wide. Males not observed. Genital extremity of female rather bluntly 

 truncated, with genital orifice posterior but near the dorsal edge of the 

 posterior end. 



Comparison. T. pectinarius differs from T. brevis, the only other 

 known member of the genus in ( 1 ) the extreme regional specialization 

 of its proboscis hooks, (2) the number of hooks on the proboscis, and 

 (3) the size of the embryos. 



Genus FILISOMA Van Cleave, 1928 



The genus Filisoma was proposed by the present writer for a concept 

 based on Filisoma indicum, a species found in the intestine of a fish, 



