80 BNTOZOA. 



other. In Heterocheilus tlie surface of the body is not clothed with 

 spines, but the mouth in both sexes is formed, as it were, by the 

 approximation of two dissimilar, three-cleft chitinous lips, whilst 

 the tail of the male terminates in a strongly curved and sharply 

 pointed hook. The other genera have spinous, or other peculiar 

 developments about the head. In regard to Curling's genus Dac- 

 tylius, of which a more particular account will be given hereafter, 

 one might at first be disposed to place it with the Cheiracanths, 

 to which it certainly bears a very striking resemblance, but the 

 absence of any spicule in the male, its pulsating dorsal vessel, and 

 other annulose characters, clearly show that it cannot be regarded 

 as a true helminth. 



Genera. — Gheiracanthus, Diesing ; = Gnathostoma, Owen ; 

 LiorJiyncJhus, Rudolphi ; = Goezia and Gochlus, Zeder ; Lecano- 

 cephalus, Diesing; Ancyr acanthus, Diesing; Aspidocephalus, Die- 

 sing; Heterocheilus, Diesing; = Lobocephalus, Diesing; Echino- 

 cephalus, Molia ; Hystrichis, Dujardin ; Hystrignathus, Leidy ; 

 Conocephalus, Diesing ; Ancyracanthopsis, Diesing ; Maphoce- 

 phalus, MoHn ; Stenodes, Dujardin ; Gosmocephalus, Mohn. 



Ascaridm. — By placing within this family only those genera, the 

 members of which display a conspicuous trivalved mouth, coupled 

 with a double spiculum in the male, we necessarily reduce it to very 

 narrow limits. I think this is an arrangement which ought to be 

 allowed to stand, whatever mode of Nematode classification be 

 finally adopted. In the typical genus the valves form three nearly 

 equally developed, prominent, convex lobes which, meeting in the 

 centre, form, in the closed condition of the mouth, a triquetrous 

 groove, whose margins are sometimes denticulated. In Eete- 

 rahis the valves are less prominent and unequal. Associated with 

 these characters we find the body more or less narrowed and acu- 

 minate at either extremity ; the surface is finely striated trans- 

 versely, and there are generally distinct indications of two or four 

 longitudinal, relatively equidistant lines passing from head to tail. 

 These fines correspond with the water-vascular and nervous sys- 



