604 



13. Erichthonius difformis, M.-Edw. 



(PI. 210, fig. 1). 



Erichflioniits difforniif:, Milne-ICdwanls, Ann. d. So. Nat. XX, p. 282. 



Syn.: Podocerns ]^eacliii, Kreyer 

 » Cerapus difformiB, Sp. Bate. 

 » Cerapus longinianus, Boeck. 



Body much more slender than in the preceding species, especial!}' in 

 the male, ('ephalon witli the frontal part very much produced, lateral lobes 

 comparatively small and rounded at the tip. Coxal plate.s in female nearly 

 as in U. nbclilus: 2nd pair in male much larger than any of the others, and 

 subelliptical in form. Eyes comparatively small, rounded, with dark red 

 pigment. Antennae rather elongated, and less densely setiferous than in the 

 said species, the last 2 peduncular joints of the superior ones about eiiual- 

 si/ed. Gnathopoda in female nearly as in E. ohclifus; the posterior ones in 

 male exceedingly elongated, exceeding, when fully extended, half the length 

 of the body, carpus nearly 3 times as long as it is broad, and slightly instricted 

 in the middle, thumb-like process rather elongate and nearly straight, some- 

 times smooth, sometimes with a very small tooth-like projection on the upper 

 edge at some distance fi'om the tip; propodos rather narrow, with the lower 

 edge sinuated in the middle, and having at the base an obtuse projection; 

 dactylus densely setiferous at the tip and the inner edge. Basal joint of the 

 2 anterior pairs of pereiopoda less expanded than in J?. ah(Ji/iig; the 3 posterior 

 pairs more slender. Uropoda and telson nearly as in that species. Bodj' 

 greyish white, more or less densely mottled with dark brown pigmentary 

 spots. Length of adult female 4 mm., of male f) mm. 



RemarJis. — This is the species upon which Milne-Edwards founded 

 his genus EricJifhoniiis. The Podocerns Lcachii of Kroyer is identical with 

 this form, and I am unable to distinguish the Cerapus longimanns of Boeck 

 as a distinct species, agreeing, as it does, in all anatomical details with adult 

 male specimens of the present species. The accessor}' small denticle on the 

 carpal process is now present, now wanting, and cannot therefore be adduced 

 as a specific mark. The form recorded by Goes from Spitsbergen as E. dif- 

 formis, is most probably not this species but E. megahps G. 0. Sars. The 

 species may be easily distinguished by its very slender form, the small size 

 of the eyes, and by the stucture of the posterior gnathopoda in the male. 



Occurrence. — I have met with this form in several places both on 

 the south and west coasts of Norway, at least to the Trondhjemsfjord. It is 



