288 On a neio Nematode from tlie Norwegian Beaver 



Discussion. 



The only nematode parasite hitherto found in the stomach 

 of Castor fiber is that recorded by Morgan in 1868. Tliis 

 autlior wrote : — " In the stomach of the beaver I have found 

 a very fine filamentous worm 40'" in length, species unknown." 

 It is difficult to determine the character of Morgan's parasite, 

 but Hall has tentatively placed it in the genus Gongylonema 

 because of its habitat and length. The parasite described in 

 this paper is placed in a new genus which has been named 

 Travassosius , in recognition of Dr. Travassos's work on the 

 Trichostrongylidaj. 



The genus may be defined as follows : — 



Trichostrongylinaj : small and slender, reddish in colour in 

 the fresh condition. Head small, with three lips. Cuticle 

 longitudinally striated except close to the head, where it is 

 transversely striated. Cervical papillge prominent. Buccal 

 cavity not well defined. Bursa with large lateral lobes 

 without a well-developed dorsal lobe. Ventral rays widely 

 separated, of very different thickness ; the ventro-ventral is 

 thin and directed ventrally ; the latero-ventral is thick and 

 in close relation with the lateral rays. The tip of the externo- 

 lateral ray is directed ventrally at its tip. The medio-lateral 

 strikes the edge of the bursa at right angles, while the postero- 

 lateral ray has its tip directed dorsally. Dorsal ray long and 

 slender, cleft at the end. Each bifurcation ends in two 

 prongs. Spicules short, twisted, with a knob-like caudal 

 end. There is no accessory piece. Prebursal papillae large 

 and conspicuous. Uteri divergent. Ovejectors well deve- 

 loped. Vulva in the posterior half of the body. Eggs of 

 moderate size, thin-shelled, colourless, and are deposited in 

 the morula-stage of development. Parasitic in tiie stomach. 



Type-species, Travassosius rufas from the European beaver, 

 Castor fiber. 



The genus is allied to Gooperia, Ransom, 1907, being 

 differentiated from it, however, by the following characters : — 

 In Cooperia the cervical papillse are absent, while in Travas- 

 sosius they are present and very prominent. In Cooperia 

 the dorsal lobe of the bursa is more or less distinctly separated 

 from the lateral lobes, while in Travassosius there is no such 

 vseparation. In Cooperia the externo-lateral ray turns back- 

 wards, while in Travassosius it turns forwards. In Cooperia 

 the prebursal papillae are absent, while in Travassosius they 

 are present. In Cooperia each main branch of the dorsal 



