290 BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



Genus HISTIOCEPHALUS Diesing, 1851 



Generic diagnosis. — Schistorophinae (p. 284) : Head provided with 

 4 small lips with submedian papillae. Posterior to the lips 2 tough 

 lateral appendices, each divided into numerous branches; each 

 branch may or may not be subdivided into processes at its free end. 

 Cervical region swollen into a bulla consisting of numerous longi- 

 tunidal folds. Male with large caudal alae with pedunculated papil- 

 lae of which 4 pairs are preanal. Spicules equal or unequal. Female 

 with vulva in anterior part of body. 



Parasitic under the tunic of gizzard of birds. 



Type species. — Histiocephalus laticaudatus (Rudolphi, 1819) Dies- 

 ing, 1851. 



This genus was placed in the Acuariinae by Skrjabin (19166) on 

 the basis of the caudal papillae and the ornaments of the head. 

 Gendre (1921&) states that because of the lip structure, the genus 

 belongs in the Spiruridae rather than the Acuariidae. Travassos 

 (19205) has not included the genus in his classification. The present 

 writer has assigned it to the Schistorophinae in consideration of the 

 nature of the very striking cephalic ornamentation. 



KEY TO SPECIES OF HISTIOCEPHALUS 



Head with 12 processes, each ending in a simple point ; spicules unequal, the 

 left 700m long, the right 155/t long Histiocephalus tridens, p. 291. 



Head with 20 to 24 processes, each ending in 2, 3, or 4 branches; spicules equal 

 (6 mm. long) Histiocephalus laticaudatus, p. 290. 



HISTIOCEPHALUS LATICAUDATUS (Rudolphi, 1819) Diesing, 1851 



Synonyms. — Spiroptera laticaudata Rudolphi, 1819; Filaria lati- 

 caudata Schneider, 1866; Dispharagus laticaudatus (Rudolphi, 1819) 

 Dujardin, 1845. 



Hosts. — Primary: Gallus gallus and Otis tetrax; secondary: Un- 

 known. 



Location. — Under the lining of the gizzard. 



Morphology.— Histiocephalus (p. 290) : Head (fig. 354 a and b) 

 with 2 semicircular chitinous rings, each bearing 10 to 12 posteriorly 

 directed chitinous appendages, which terminate posteriorly in 2, 3, 

 or 4 branches; these appendices are approximately equal in length 

 and in the male may measure 55 to 66/*. Posterior to this structure 

 the neck is swollen by a series of thick longitudinal ridges. There 

 are 4 small hemispherical lips, the lateral bearing 2 very small 

 papillae ; there are 4 submedian papillae. 



Male 5 to 11 mm. long by 100 to 200/* wide, or to 340/*, according 

 to Skrjabin (fig. 355). Posterior extremity of body spirally twisted, 

 according to Molin, slightly enlarged and provided with 2 caudal 



