MAZATLAN UNIVALVES 281 



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= Crepidula unguiciilus, var. Brod. in Mus. Cum. — [lanacus 

 tmguiculus, Sow. ?ubi) S. 8f A. Ad. Gen. i. 370. 



? = Crepidula Patagonica + C. protea, D'Orb. (pars,) B. M. Cat. 

 Moll. p. 48, no. 416, 417. 



Comp. Crepidula Navicelloides, JVutt. in Ja2/'s Cat. p. 107, 

 no. 3035, (Upper California.) 



Comp. Crepidula cxplanata, Gould, Cal. Sf Mex. Shells, p. 4, 

 pi. 14, f. 7. = Cal^Titraa perforans, Val. Voy. Ven. 1846, pi. 24, 

 f. 9, 9 a, h. [The author seems to imply that the creature 

 burrows : the specimen Tepresented however has evidently 

 been developed in the hole of a Lithophagus.] = C. exuviata, 

 Ntitt. in Jay's Cat. p. 107, no. 3027. 



This creature, when flat and finely grown, is the C. squama 

 of Brod. The same shell, when coarsely gi-own, more convex 

 and without brown stripes, is the C. nivea of C. B. Ad. "When 

 the layers of which C. nivea is composed, instead of lying 

 regitiarly one over the other, are slightly prominent, it becomes 

 the C. striolata, Mke. "When tbey arc di-awn forwards and 

 project, it becomes the C. Lessonii, Brod. The name of Prof. 

 Adams is retained, in preference to the prior ones of Broderip 

 and Menke, as representing the normal condition of the shell. 

 The name C. unguiculus has priority, but does not ai^pear to 

 have been published. Among tke specimens marked C. protea 

 and C. Patagonica by D'Orb. in his collections, there are 

 several which seem to belong to this species ; others to C. onyx, 

 &c. V. supra. Both arc refei'red by Dr. Gray to C. ddatata, 

 (B. M. Cat. D'Orb. Moll. p. 49.) 



C. nivea begins life as a minute Velutina-shaped body, with 

 a sunken apes and coarse concentric folds. When this has 

 grown to about '015 across, it suddenly enlarges itself, throws 

 a columellar lip over the base of the shell, raises a more or less 

 prominent margin round it, so as to surround the vertex, and 

 commences its septum at an angle from the columellar lip 

 varying from about 90° at the posterior to 130° at the anterior 

 end. The smallest shell found measures "Olo in length, on 

 which these stages are distinctly traceable. The septum is at 

 first straight, then angulated in the middle, lastly with an 

 anterior sinus. 



In the 'squama' stage, it appears as a very thin flat shell ; 

 with the vertex generally lustrous brown, sometimes white ; 

 from this radiate a greater or less number of brown lines, 

 sometimes more or less broken into dots, gradually losing 



