THE NEMATODE FAMILY GNATIIOSTO.MID.E. 



291 



worms from the intestine of a fonr-spined sting-rny, Aetobatis 

 narinari^ from Loyalty Islands. I'^he name E. sti'latits, however, 

 seems to be a nor.ieii nudum, and we liave no means of identify- 

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

 pleteness. Shipley (l. c.) gives a figure of the head of the form 

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

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

 our E. southwelli, a,nd is possiblj^ identical v/ith it. 



GNATHOSTOMA* Owen, 1836. 



Gnathostoma Owen (1836, p. 125). 

 Cheir acanthus Diesing (1838, p. 189). 



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



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



(1905, p. 54)]. 

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

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

 Giiathostomum Mitter (1912, p. 150). 



The members of this genus are stout worms with the chai'acters 

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

 contraction of the contained muscles, globular or somewhat 

 llattened antero-posterioily, and bears in the known species from 

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

 Ecldnoceplialu.s, set on a cuticle which shows no external trace of 

 the four underlying ballonets. Some of the anterior and posterior 

 rows may be obscured, the first l)y the inrolling of the anterior 

 part of tlie head-l)ulb, 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 denselv set 

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

 more or less alternately in transverse rows and ha^-e their free 

 orlges indented to vaiying degrees, so that they come to possess 

 sluirp points of varying shape and number. Towards the middle 

 of the body the spines become simple and eitlier continue as such 

 to the posterior end or progressively diminish in size and finally 

 disappear, leaving the posterior part of the body naked. The 

 excretory pore has not been detected, a. failure easily understood 

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

 ness of the pore in other genera of the sul)family. 



Tlie male has lateral caudal ala? eacii sustained by four large 

 papillae and by the tip of the tail, wliich has the general appearance 

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

 papilla (Schneider. 1866, p. 86 and tt'xt-fig. ; v. Linstow, 1893, 

 p. ^06, fig. 11). Between the ahe are two |)airs of small, sessile, 

 ventral papillae. The male has two uiiequal spicules and no 

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

 descril)ed, lying veniralhj to the spicules, a iKjdy which he seems 

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



For generic diagnosis, see p. 292, 



Pjroc. Zool. Soc— 1920, Xo. XX. 20 



