THE NEMATODE FAMILY GNATHOSTOMIDiE. 273 



mucous membrane, and very tightly adhering by means of the 

 one or two constrictions." 



The form thus described by Leidy so strongly suggests a 

 Tanqua, both on account of several points in the brief descrip- 

 tion and on account of its host and habitat, that we feel obliged 

 to include it in our account of the genus. It is impossible, how- 

 ever, without further investigation, to assign it to a definite 

 position. 



ECHINOCEPHALUS * Molin, 1858. 



Echinocephalus Molin (1858, p. 154). 

 _ „ (1861, p. 311). 

 Cheiracanthus (in part) v, Linstow, in Shiplev and Hornell 

 (1904, p. 100). 

 ,, (in part) v. Linstow, in Shipley and Hornell 



(1905, p. 54). 



Molin's original generic diagnosis was as follows : — 



" Caput discretum, echhnatum ; os orhiculare, terminale, maynimi, 



inerme, vel armatum; corpus cylindricum, inerme, vel echinatum ; 



vagina penis dipetala ; [jxnus lateralis t]. — Avium et 2nscium endo- 



parasita." 



Under this generic name two species were originally enume- 

 rated by Molin, E. uncinatus and E. cygni. The latter was 

 regarded as a species inqicirenda, leaving E. uncinatus the un- 

 disputed type-species. E. cygui belongs to the genus Hystrichis, 

 and is, in fact, a synonym of //. pachycepjhalus Molin. Into the 

 affinities of Hystrichis it is beyond our present scope to enter, 

 but in spite of the rather strong superficial resemblance borne by 

 some of its species to some of the Gnathostomida^, we regard it as 

 being of quite a different type from this group. Molin's generic 

 characters for Echinocephalus seem, however, to have been based 

 in part on the characters of E. cygni, and for this reason it 

 becomes necessary to emend the diagnosis, besides adding to it 

 from our own observations (see p. 275). Thus the " os orhiculare " 

 and the statement that the genus is parasitic in birds as well as 

 in fishes belong rather to Hystrichis tha.n to Echinocephalus. 



Molin (1861) rightly suggests the relationship of this genus 

 to Cheiracanthus (i. e., Onathostoma). It shows equally great 

 resemblances to Tanqua, and may, in fact, be looked upon as a 

 Tanqua-\\ke form complicated by the development of rows of 

 spines or hooks along the cuticular ridges or " striations " of the 

 head-bulb. 



The lips are, in most cases, very similar in plan to those of 

 Tanqua, and show a similar interlocking arrangement of the 

 internal, tooth-like, cuticular ridges. In one form, however, the 

 arrangement is complicated by the multiplication of the teetli on 



* For generic diagnosis, see p. 275. 

 t Added in 1861. 



