484 MAZATLAN UNIVALVES 



Genus EAPANA, Schum. 

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



Subgenus EHIZOCHEILUS, Sieens. 



Steenstmp, Afh. Ac. Copenh. May, 1850.—^. Sf A. Ad. Gen. 



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

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

 Murex, pars, et Purpiira, pars, auct. 



611. Ehizocheilus nux, Rve. 



Murex niLx, Rve. Conch. Ic. pi. 35, sp. 181 : (diagn. nunc auct.)* 

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

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



R. t. valde solida, irregulari, alba; anfr. oiucleosis feevibus, 

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

 tibus Y .-Vin. tumidis, rotundatis, plus viinusve prominentihus ; 

 liris confertis spiralibus squaniosis, interstitiis profundis, plus 

 minusve angustis ; sqitamulis covfertissimis, rotundatis : aper- 

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

 lato; labio hand tenui, hand producto ; canali angustd, profunda 

 excavatd, rccurvatd ; costd canaliferd solida, intortd, rimam 

 umbilicalem monstrante : operculo subpyriformi, nigro-fusco, 

 margine tenui, diaphano ; nucleo in mai'ginis externi medio 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 Vitularia salebrosa and 

 Cuma costata, more nearly approaching the latter. Although 

 only bearing a general resemblance to the tj-pical Ehizocheilus, 

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

 the subgeneric name Coralliophila) form a natural assemblage 



• The species in this ^oup are so similar to each other, but the shells in each 

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

 as the types in Mus. Cuming have been so corroded by the acid process that the 

 minute sculpture (which is one of the best criteria) is no longer visible. The 

 type of Murex nux, Heeve, may therefore stand for whatever is wished : the 

 Mazatlan shell is called after it on Mr. Cuming's authority. The Panama shell 

 broufjht by Jlr. Bridges (at first named K. distans, Wr. Cuming regarding them 

 us distinct) appears to be one among the many varieties of "R. niveus, .1. Ad." : 

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

 The R. Califoruicus may bo distinct, having a very large body whirl, witli the 

 ribs almost obsolete ; but this again has lost its markings under the acid. [The 

 Leueozonia Californica, Uulf of Ca\. Zieid. ShipUi/, appears more nearly allied 

 to LathirusthBu to Leucozoniaciugulata.] 



