10 PROCEEDINGS OP THE NATIONAL. MUSEUM vol.81 



These species also differ in the length of the spicules; in A. scolecl- 

 formis they are about 905/x long, in A. fasciata about 360/x, long, in 

 A. raillieti about 760^ long, and in A. hm'woodi^ 1.15 mm to 1.29 

 mm long. In A. scoleciformis and A. rmlUeti the tail of the male 

 is about 360/^ long, whereas in A. fasciata it is only 270/a and in A. 

 harwoodi 450ju, to 560/x. 



CRUZIA TENTACULATA (Rudolphi, 1819) 



This species has been recorded from a number of species of Didel- 

 phis in Brazil and also from D. mrginiana in Pennsylvania, although 

 Travassos (1922) says that it is not impossible that the North Amer- 

 ican species is different from the South American. The Texas speci- 

 mens, however, agree very closely with Travassos's description of 

 C. tentaculata in anatomical details, and all the measurements fall 

 within or very close to the range given by Travassos. Specimens of 

 the same genus have been found by P. D. Harwood (not yet pub- 

 lished) in great abundance in the large intestine of box turtles {Ter- 

 ra-pene Carolina t?iunguis), and these specimens also agree very 

 closely with O. tentaculata; their separation into a distinct species i& 

 based on characters of doubtful validity. 



PHYSALOPTERA (TURGIDA) TURGIDA Rudolphi, 1819 



This species has been recorded in a considerable number of species 

 of Didelphis^ both in North and South America. It is a very common 

 parasite, and has been found absent in only one opossum examined 

 in the vicinity of Houston, Tex. 



GNATHOSTOMA DIDELPHIS, new species 



Diagnosis. — Large, stout worms, tapering only slightly at the 

 ends. Length 25 mm to 34 mm, with a maximum diameter of 1 mm 

 to 1.25 mm. Lips large, thick, trilobed. Head bulb 650/x, to TOO|U, 

 broad and about 300ju, long, armed with 9 to 11 rows of spines similar 

 in size and shape to those of G. spinigeruni. Cuticle provided with 

 densely set, comblike spines or scales anteriorly, these disappearing 

 somewhat anterior to the middle of the body. Shortly behind the 

 head bulb the thick basal portion of the scales is 30/a to 35/* broad, 

 while the thin projecting portion, or blade, is relatively short 

 and very broad; its truncated distal end, 55/x, to 65/1 broad, is pro- 

 vided with from 8 to 12, sometimes even 14, small irregular points. 

 (Fig. 5, A.) After a few rows the blade begins to elongate in the 

 middle and becomes leaf-shaped, with about eight large, coarse 

 spines. (Fig. 5, B.) Some of these scales have blades 40/i to 50/i 



