334 BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



genus, the result being that these species had to be grouped to- 

 gether as of uncertain subgeneric classification. It has therefore 

 been deemed advisable to reduce the descriptions, in raising the sub- 

 genera of Travassos to generic rank, to the basis of the difference in 

 female body form, and thus be able to assign all the species of Tetra- 

 meres (sensu lato) to one of the two genera, Tetrameres or Microte- 



Genus TETRAMERES Creplin, 1846 



Synonyms. — Tropisurus Diesing, 1835; Tropidurus Wiegmann, 

 1835; Tropidocerca Diesing, 1851; Astomwn Schlotthauber, 1859; 

 Acanthophorus Linstow, 1876. 



Generic diagnosis. — Tetrameridae (p. 333) : Female body globular 

 or spindle-shape, with 4 longitudinal furrows corresponding to the 

 median and lateral lines. 



Type-species.— T etrameres paradoxa (Diesing, 1835) Travassos, 

 1914. 



KEIY TO SPECIES OF TETRAMERES 



1. From Fulica atra; anus 220/* from posterior extremity; eggs 39/* long by 



29fi wide Tetrameres globosa, p. 346. 



From other hosts than Fulica atra, or if from that host, anus 71/t from 

 posterior extremity and eggs 48 to 56/* long by 26 to 30/t wide (Tetra- 

 meres fissispina) 2. 



2. Mouth of female surrounded by 3 projections, each of which bears a thorn 



on its outer and on its inner surface ; male unknown, female poorly 



described; in Corvus comix Tetrameres unispina, p. 351. 



No such structures described on female mouth ; male known in all but two 

 species and female more fully described than above ; in other hosts 

 than Corvus comix 3. 



3. Female 7 mm. long by 7 to 8 mm. wide ; male 12 to 18 mm. long, its caudal 



extremity said to be alate Tetrameres certa, p. 338. 



Female smaller than above or if as large (T. gynaecophila), the male is 

 smaller than that of above and has no caudal alae 4. 



4. Female 5 mm. to 13 mm. long by 4 to 7 mm. or more wide, or larger ; male 



6.5 to 15 mm. long 5. 



Female not over 4.5 mm. long (except in T. confusa and T. fissispina 

 which may reach 5 and 6 mm. long respectively) ; male, when known, 

 not over 6 mm. long 7. 



5. Female 6.75 to 8 mm. long by 4.5 to 7 mm. wide; male 11 to 15 mm. long; 



spicules 3 mm. and 468/t long respectively Tetrameres paradoxa, p. 335. 



Female usually smaller or larger than above ; male not over 10 mm. long ; 

 spicules much smaller than above, or said to be absent 6. 



6. Female not over 6 mm. long by 5 mm. wide ; male with 4 longitudinal series 



of spines ; spicules 740/* and 16/* long respectively. 



Tetrameres gigas, p. 345. 



Female 8 mm. long by 7 mm. wide, or larger ; male without spines ; spicules 



said to be absent Tetrameres gynaecophila, p. 347. 



7. Anus of female 332/*, cloacal aperture of male 232 to 290/* from posterior 



end Tetrameres americana, p. 337. 



Anus of female and cloacal aperture of male both nearer to the posterior 

 end than above 8. 





