A NEW SPECIES OF ROUND WORM OF THE GENUS TRI- 

 CHOSTRONGYLUS FROM THE RABBIT 



By H. W. Graybill 



Of the RockefeUer Institute for Medical Research 



In making autopsies on two wild rabbits of Princeton, N. J., an 

 aj)parently undescribed species of Trichostrongylus was found in 

 the large intestine of one. In addition to this nematode, it will be 

 of interest to note that both rabbits w^ere infested with OheJiscus 

 cunlculi, a new genus of nematode which the writer described from 

 the domestic rabbit^ and with Trichostrongylus calcaratus Ransom, 

 1911. The latter species has also been collected here from one of 

 our domestic rabbits kept for experimental purposes. 



So far as the writer has been able to determine, three species of 

 Trichostrongylus have been described from rabbits: T. retortaeformis 

 (Zeder, 1800) Loos, 1905; T. pigmentatus (von Linstow, 1904) Hall, 

 1916; and T. calcaratus Ransom, 1911. 



TRICHOSTRONGYLUS AFFINIS. new species 



Male. — The maximum width of the body occurs at the base of the 

 bursa. From there it tapers uniformly to the anterior end. Length 

 5-7.5 mm., maximum width 123[x, width of head 12iJL. The anterior 

 end is rounded. The esophagus is broadest near the posterior end 

 and tapers gradually anteriorly. Its length is 562-787[jl, maximum 

 width 27[x, and the nerve ring 127[x from the anterior end. 



The lateral lobes of the bursa are rolled inward in preserved 

 specimens, making it very difficult to observe the shape and arrange- 

 ment of the raj's. A dorsal lobe has not been observed. The ventro- 

 ventral and externo-dorsal rays at their distal ends curve ventrally 

 and dorsally, respectively (fig. 1). The other rays lie close together. 

 The externo-lateral ray is very broad, the latero-ventral ray is not 

 so broad, and the postero- and medio-lateral rays are relatively 

 narrow. The dorsal ray divides distally into two short branches. 

 The spicules and gubernaculum are brown in color. The spicules 

 are about equal, short, stout, curved ventralty, and at the proximal 



' Parasitology, vol. 15, No. 3,. p. 340, 1923. 



No. 2548.— Proceedings U. S. National Museum, Vol. 66, Art. II. 



100460—24 1 



