138 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



the position of the vulva near the anus, and the length of the spicule 

 in Thaparia seem sufficient to exclude the Galapagos species from this 

 genus. 



The genus Alaeuris is characterized by Thapar (1925) as follows: 

 "Oxyurids of small or medium size; simple lips; both lateral and caudal 

 alae present, the latter very prominent; vulva behind the middle of the 

 body; ovejector present terminating in a bulb; uteri two; spicule single; 

 accessory piece present; only pre-anal papillae pedunculated, others 

 sessile." 



Four of the five species of nematodes from the Galapagos land 

 iguana are apparently of the genus Alaeuris. These four species agree 

 with the generic diagnosis as given by Thapar except for one character- 

 istic, namely, the lateral alae do not seem to be present. However, Sand- 

 ground (1929) has assigned to this genus a species, A. hirsutus Sand- 

 ground, 1929 (from a Central American iguana. Iguana rhinolopha), 

 which apparently does not have lateral alae. The type species of Alaeuris, 

 A. alaeuris Thapar, 1925, has lateral alae only at the posterior end of 

 the male. The second species, A. iguanae Thapar, 1925, apparently 

 possesses lateral alae, but no mention is made of them in the specific 

 diagnosis, and no figures show them. 



Until 1933, then, only one of the three species of Alaeuris has well- 

 defined lateral alae, one is doubtful, and the third apparently lacks them. 

 A nematode from Testudo verreauxi of South Africa was assigned to 

 the genus Alaeuris by Ortlepp in 1933. This species, A. conspicua Ort- 

 lepp, 1933, possesses well-developed lateral alae in both sexes. The 

 species from the Galapagos land iguana are like A. hirsutus in respect 

 to the absence of lateral alae. Since this is the only important character- 

 istic in which the Galapagos forms differ from the diagnosis of Alaeuris, 

 and it is evident that there are various degrees of development of this 

 characteristic within the known members of the genus, this characteristic 

 does not seem to be of sufficient importance to exclude the four Gala- 

 pagos species from the genus Alaeuris. Consequently, four of the five 

 species of nematodes from the Galapagos land iguana are assigned to the 

 genus Alaeuris Thapar, 1925. The fifth species in the collection is con- 

 sidered to represent a new, but rather closely related genus. Its relation- 

 ship will be pointed out with its description. 



Type specimens are deposited in the United States National Museum 

 and in the Allan Hancock Foundation at The University of Southern 

 California. 



