THE NEMATODE FAMILY GNATHOSTOMID.E. 291 



worms from the intestine of a four-spined sting-ray, Aetohatis 

 narinari, from Loyalty Islands. Tlie name E. striatus, howevei-, 

 seems to be a nomen nudum, and we have no means of identify- 

 ing the species, though we mention it here for the sake of com- 

 pleteness. Shipley [1. c.) gives a figure of the head of the form 

 referred to by him, and in this figure some 14 rows of hooks are 

 indicated, so that his species would seem to approach closely to 

 our E. southtvelli, a,nd is possibly identical with it. 



GNATHOSTOMA* Owen, 1836. 



G imthostoma Owen (1836, p. 125). 



Cheiracanthtcs Diesing (1838, p. 189). 



,, Diesing (1839, p. 221) [not Cheiracccnthtts Diesing 



of V. Linstow, in Shipley and Hornell (1904, p. 100) nor 

 (1905, p. 54)]. 



Filaria (in part) Schneider (1866, p. 98). 



Cheiranthus v. Linstow (1893, p. 202) [misprint], 



Gaathostoiymm Mitter (1912, p. 150). 



The members of this genus are stout worms \yith the charactei'S 

 of the subfamily. The head-bulb is, according to the state of 

 contraction of the contained muscles, globidar or somewhat 

 flattened antero-posteriorly, and bears in the known species from 

 eight to twelve transverse rows of simple hooks, like those of 

 EcliinoGephalus, set on a cuticle which shows no external trace of 

 the four underlying ballonets. Some of the anterior and posterior 

 vows ma,y be obscured, the first by the inrolling of the anterior 

 part of the head-bulb, as the result of contraction of the internal 

 muscles, the second by the partial retraction of the head-bulb 

 into the neck and the resulting interposition of the densely set 

 .scale-like spines which cover this part of the body. These are set 

 more or less alternately in transverse rows and have their free 

 eilges indented to varying degrees, so that they come to possess 

 sharp ])oints of varying shape and number. Towards the middle 

 of the body the spines become simple a,nd either continue as such 

 to the posterior end or progressively diminish in size and linally 

 disappear, leaving the posterior part of the bod}'' naked. The 

 excretory pore has not been detected, a failure easily undei'stood 

 when one considers the dense covering of spines and the minute- 

 ness of the pore in other geneiu of the subfamily. 



The male has lateral caudal alse ea.eh sustained by four large 

 papilke and by the tip of the tail, which has the general appea.ra.nce 

 of, and has sometimes been counted as, an unpaired terminal 

 papilla (Schneider, 1866, p. 86 and text-fig.; v. Linstow, 1893, 

 p. 206, fig. 11). Between the alas are two pairs of small, sessile, 

 ventral papillae. The male has two unequal spicules and no 

 ficcessory piece, although v. Linstow (1893, p. 206, fig. 13) has 

 described, lying ventrally to the spicules, a, body which he seems 

 to regard as such, calling it a " StUtzapparat." 



* For generic dingiiosis, see p. 292. 



Proc. Zool. Soc— 1920, No. XX. 20 



