NO. 15 VAN CLEAVE : ACANTHOCEPH ALA 509 



Types. Description based on 10 individuals (6 males, 4 females) of 

 which one male (VC 3125.2) designated as holotype and 2 paratypes 

 are deposited in the Allan Hancock Foundation of The University of 

 Southern California; allotype female (VC 3125.1) and 2 paratype males 

 in the collection of H. J. Van Cleave, Urbana, Illinois; and one male 

 and one female paratype in the U.S. National Museum. 



Specific diagnosis. Gorgorhynchidae without body spines. Mature 

 females about 60 mm long, males about 45 mm. Body very much attenu- 

 ated, slightly enlarged just posterior to the posterior tip of the receptacle, 

 in females about 0.6 to 1 mm in diameter for most of its length; in 

 males about 0.4 to 0.6 mm. Proboscis long, cylindrical, about 1.5 to 2 

 mm long, slightly to strongly arcuate, armed with 16 longitudinal rows 

 of 38 to 45 hooks each. The median dorsal row of hooks differentiated 

 from all the remainder in that they lack sharp points but each ends in a 

 blunt tip of hornlike appearance. Near the middle of the length of the 

 proboscis the ventral hooks are stout, sharp, strongly recurved, about 

 57 ju, long and 21 ix in diameter at the base; on the dorsal surface hooks 

 in the median row are bluntly pointed, 57 /a long, 21 /* in diameter at 

 base ; dorsal but lateral to the median row the hooks are simple, slender, 

 sharp pointed, about 43 to 51 /a long by 9 ju. in diameter at base. Papillae 

 not observed on neck or proboscis. Proboscis receptacle double walled, 

 very long (2.3 mm to 4.2 mm), with brain located at base and retinacula 

 emerging from its posterior tip. Lemnisci fairly heavy, often almost as 

 broad as receptacle, approximately the same length as receptacle. 



Male genitalia restricted to approximately the posterior half of the 

 body. The 2 testes elongate, slightly separated, followed by a series of 

 4 very long, tubular cement glands. 



Posterior extremity of female obliquely truncated in posterior-dorsal 

 area, with the female orifice subterminal on the dorsal surface. Embryos 

 within body cavity of mature female 56 to 69 yx long by 12 to 18 /a wide. 



Comparison. F. bucerium differs from the other 2 species of the 

 genus Filisoma in the presence of one middorsal longitudinal row of 

 conspicuously modified, heavy, blunt, hornlike proboscis hooks and in 

 the possession of a larger number of hooks in each longitudinal row than 

 in any other species. 



Of the 2 previously described species, F. indicum has been recorded 

 from India only, while F. microcanthi rests on a single record from 

 Formosa. F. bucerium is the first species described from the Western 

 Hemisphere. 



