484 MAZATLAN UNIVALVES 



GENUS EAPANA, Sehum. 

 Essai, no. 57, 1817. Shell Pyndoid : operculum Purpuroid. 



SUBGENUS EHIZOCHEILUS, Steens. 



Steenstrup, Afh. Ac. CopenJi. May, 1850, JT. $ A. Ad. Gen. 



vol. i. p. 135 ; (diagn. auet.) 

 Eapana, pars, Phil. Handb. Conch, p. 487. 

 Murex, pars, et Purpura, pars, auct. 



J^ 611. EHIZOCHEILUS NUX, Eve. 



Murex nnx, five. Conch. Ic. pi. 35, sp. 181 : (diagn. mine auct.)* 

 Murex (Ocinebra) nux, H, fy A. Ad. Gen. i. 75 : [non Purpura 



(Polytropa) nux, loc. cit. i, 128.] 



It. t. valde solidd, irregulari, alba ; anfr. nucleosis Icevibus, 

 primo decollato ; spird seu depressd, sen elevatd ; costis radian- 

 tibus v.-viii. tumidis, rotund atis, plus minusve prominentibus ; 

 liris confertis spiralibus squamosis, interstitiis profundis, plus 

 minusve angustis ; sqiiamulis confertissimis, rotundatis : aper- 

 turd ovoided, labro acuto, a squamuhs crenulato, intus denticu- 

 lato ; labio haud tenui, haudproducto ; canali angustd, profunde 

 excavata, recuvvatd ; costd canaliferd solidd, intortd, rimam 

 umbilicalem monstrante : operculo subpyriformi, nigro-fusco, 

 mdrgine tenui, diaphano ; nucleo in marginis externi inedio sito. 



That this curious and very variable shell is not a Murex, is 

 shewn by its Purpuroid operculum and want of varices. It is 

 intermediate in character between Yitularia salebrosa and 

 Cuma costata, more nearly approaching the latter. Although 

 only bearing a general resemblance to the typical Ehizocheilus, 

 yet as the species brought together by Messrs. Adams (under 

 the subgeneric name Coralliophila) form a natural assemblage 



* The species in this group are so similar to each other, but the shells in each 

 o variable, that their discrimination is a matter of extreme difficulty : especially 



, 

 as the types in Mus. Cuming have been s 



rroded by the acid process that the 



urougnt oy irtr. x>riages ^ai nrsi namea xt. aistans, ivir. turning _ _ D __ 



as distinct) appears to be one among the many varieties of "K. niveus, A. Ad." : 

 nor doe?, the acid allow of a distinction being evident between this and R. nux. 



