12 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



Female^ 25 to 34 mm long with a diameter of from 1 to 

 1.25 mm. The vulva is situated slightly behind the middle of the 

 body. The anus is about 300/* from the tip of the tail. The tail 

 is bluntly rounded, somewhat flattened ventrally when seen in lat- 

 eral view. There is a pair of large lateral papillae situated near 

 the end of the tail, about equal in size to the tip of the body pro- 

 jecting beyond them, giving the termination of the body a trilobed 

 appearance. Reproductive organs immature, and no eggs present. 



Host. — Didelphis virginiana. 



Location. — Liver. 



Locality. — Houston, Tex. 



Type specimen. — U.S.N.M. Helm. Coll. No. 8551; paratypes, 

 No. 8552. 



ReiYharks. — Gnathostomes have hitherto been recorded from opos- 

 sums by Stossich (1902), Travassos (1925), and Dikmans (1931). 

 Stossich based his meager description of Gnatliostom,a turgidum on 

 two poorly preserved females taken from Didelphis azarae in Argen- 

 tina. These worms were described as having 10 to 12 rows of spines 

 on the head bulb; cylindrical bodies 23 mm in length, tapering in 

 both directions; and spines of varying shape on the anterior half of 

 the body. Travassos obtained what he considered to be the same 

 species from the stomach of Didelphis aurita in Brazil, and rede- 

 scribed it from two males and a female. According to Travassos's 

 description the males were 38 mm and 45 mm in length and the 

 female 58 mm ; the males had a diameter of 2 mm and the female 2.5 

 mm. The body spines reach a maximum length of 160/x, with numer- 

 ous teeth, as in the species here described. There are 9 pairs of caudal 

 papillae, 1 pair ventral and adanal, the others lateral, 3 being preanal, 

 2 adanal, and 3 postanal but unsymmetrical. The shorter spicule is 

 1 mm long and 0.12 mm broad, while the longer one is 4.2 mm long 

 and 0.2 mm broad. The cloaca is 0.7 mm from the posterior extrem- 

 ity. It will be seen that this form is much larger than those described 

 here as Gnathostonia didelphis^ with much longer body spines, with 

 longer spicules with more difference in the relative length of the two, 

 and with 9 pairs of caudal papillae instead of 5. Since my specimens 

 are sexually immature and taken from the liver, in which organ they 

 evidently develop before settling in the wall of the stomach, as in the 

 case of Gnathostoma spiniger-um (Chandler, 1925b), the difference 

 in size is probably of no significance, although the differences in the 

 spicules may be. There can be little question, however, that the 

 difference in the number of caudal papillae proves my species to be 

 distinct from GnathostoTnia turgidwni of Travassos. Since the origi- 

 nal draft of this paper was written, Dilonans (1931) records finding 

 a male specimen of a gnathostome in the stomach of Didelphis 



