48 



expressly stated to be in substitution for that name, which 

 Kinahan supposed to have lapsed. Since Poniophzlus is now 

 upheld it is evident that Cheraphilus itself must lapse, and 

 the species which have been referred to it, Crangon nanus, 

 Kroyer ; C. cchinulafus, M. Sars ; and C. neglecius, G. O. 

 Sars, may be placed under the new generic name Philocheras^ 

 which has the accent on the ante-penultimate syllable. 



The name Egcmiy Risso, 1816, was preoccupied, and 

 perhaps for that reason it occurs in the altered form ^geon 

 in the writings of Guerin-Meneville, 1835 ; Kinahan, 1862 ; 

 Ortmann, 1890. The two latter authors draw a very fine 

 distinction between this genus and Po7ifophihis, namely, that 

 the latter has the rostrum pointed or somewhat rounded, 

 while in y^geon it is broadly truncate or emarginate. This 

 distinction is untenable if I am right in considering that 

 Pontocaris is a synonym of ^Egcon, for in Bate's genus the 

 rostrum is emarginate in one species and pointed in the 

 other. According to Bate the branchial formula of Pontocaris 

 differs from that of Pontophilus by not including a rudimentary 

 mastigobranchia on the third maxillipeds. He also points 

 out the interesting distinction that in Pontocaris '■" the inferior 

 extremity of each branchial plume is thrown forwards," which 

 J have verified in the case of ^Sgeou catapliractus, whereas in 

 Cra7tgon and Pontophilus the extremity is directed backwards. 

 Whether Bate's definition of Pontophilus is based on any 

 examination of the type species is left uncertain in his 

 " Challenger " report. He makes a reference, but a wrong 

 one, to the work in which the genus was instituted. In his 

 revision of " The Crustacea in Couch's Cornish Fauna," 1878, 

 he speaks of having frequently taken the type species in 

 question, and there calls it Crangon spinosus. Sars, in his 

 Essay on the Metamorphoses of the Crangonidae, notes that 

 Pontophilus has six pairs of well developed branchiae, and a 

 rudimentary pair, as distinguished from Crangon and 

 CheraphiluSy in which there are only five pairs of branchiae. 

 He further shows that between the larval forms there are 

 some very striking differences, the telson for instance in 

 Crafigon and Cheraphilus being broadly truncate, but in 

 Pontophilus variously bifid. 



Sars also shows that in the larval forms of the Crangonidae 

 the mandibles have both molar and dentate cutting edge. 

 According to Spence Bate and Ortmann it is the cutting edge 

 that disappears in the adult and the molar that remains. But 

 it seems more natural to suppose that the dentate apex of the 

 adult mandible represents the cutting edge, and that the 

 molar has disappeared, as in many other crustaceans it 

 undoubtedly does. 



