72 



BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



Morphology. — Heterakis (p. 50) : Color gray-white. Cuticle with 

 fine transverse striations. 



Male 23 to 25 mm. long by 700/* wide. Esophagus 1.125 mm. long, 

 its cylindrical part 238/* wide; bulb 272/* long by 300/* wide. Tail 

 (fig. 99) pointed, provided with caudal alae; cloacal aperture 420/i 

 from posterior end. Preanal sucker 230/* in diameter, its posterior 

 border 630/* from the caudal extremity. Thirteen pairs of caudal 

 papillae of which 2 are preanal, 7 adanal, 4 postanal. Spicules equal, 

 850/* long, whip-shaped, the anterior thicker end resembling the 

 handle of the whip and the exceedingly fine and delicate posterior 

 or free end the whip itself. 



Female 25 mm. long by 1 mm. wide. Esophagus, 1.125 mm. long, 

 its cylindrical part 200/* wide; bulb 255/* long by 272/* wide. Tail 

 conical, anus 220/* from posterior end. Vulva in anterior part of 

 body, 4.42 mm. from anterior extremity. Eggs oval, 76.5 to 85/* long 

 by 47/* wide. 



Life history. — Probably similar to that of H. gallinae (p. 54). 



Distribution. — South America (Paraguay). 



At the time that Skrjabin identified the specimens from Ti7iamus, 

 species of Paraguay as Heterakis arquata, he had not seen Travassos's 

 paper (1913) but based his identification oif Schneider's scant de- 

 scription. Travassos gave a detailed description of Heterakis ar- 

 quata, agreeing in all particulars with Schneider's description, and 

 the specimens described by Travassos were from the type locality and 

 as far as can be ascertained, from the type host, Crypturus cupreus. 

 Skrjabin's description differed from that of Schneider in the number 

 of caudal papillae, and from that of Travassos in numerous very 

 marked respects, as seen below. It has been thought advisable by 

 the present writer, therefore, to give a new name to the species de- 

 scribed by Skrjabin. 



A comparison of H. arquata as described by Schneider and Tra- 

 vassos, and of H. skrjabini as described by Skrjabin is as follows: 



H. arquata 



H. skrjabini 



Preanal sucker (diameter) _ 

 Cloacal aperture, from end 



of tail. 

 Spicules 



Caudal papillae 



Anus of female from tail 



end. 

 Vulva 



Eggs 



90 M 



270 M - 



Very long (according to 

 figuie over 2 mm.) 



12 pairs 



1.12 mm 



A little anterior to mid- 

 dle of body. 

 52m by 29m 



230m. 

 420m. 



Relatively short (850m). 



13 pairs. 

 220m. 



In anterior fifth of body. 

 76.5m to 85m by 47m- 



