MAZATLAN UNIVALVES 275 
This beautiful and rare species combines the form and habit 
of growth of the Atlantic C. porcellana, Zinn. with the very 
remote apex of C.adunca. This character also separates it from 
C. arenata, Brod. (found at 8. W. Mexico, P. P. C., but not at 
Mazatlan,) to some forms of which it bears a close resemblance. 
C. arenata occasionally develops an apical hole within, (Mus. 
Cum.): but is never seen with the very oblique growth of this 
species. The nucleus is like a regular, somewhat tumid Plan- 
orbis ; shewing the whirls within, and measuring about °02 in. 
across. The enlargement is regular, and the young shell has 
exactly the characters of the adult, except that the apex, though 
separate, is nearer the margin. Only two very young specimens 
and one adolescent were found in the Mazatlan collection; a 
larger one, probably from the same collection, was obtained 
from a shop: and some very fine ones are in the Cumingian 
Museum. The smallest specimen is ‘12 in length ; the largest 
long. °95, lat. °64, alt. ‘35. 
Hab.—Real Llejos, Cuming, teste Broderip: (but Gulf of Cali- 
fornia, teste Mus. Cum.)— Panama, 1 sp. C. B. Adams.— 
Mazatlan ; extremely rare, jun. on Spondylus; ZL’ pool Col. 
Tablet 1355 contains a young sp.—1356, an adolescent sp. 
Tank. Cat. no. 828, App. p. vi.—(Crypta a.) H. Sf Py, Gen. 
1. 369. 
=Crepidula solida, Hinds, Voy. Sulph. Moll. p. 53, no. 218, 
pl. 16, f. 7, 8.—(Crypta s.) H. gf A. Ad. Gen. i. 369. 
=Crepidula rostriformis, Gould, Hap. Shells, 1846, p. 14. 
Jun. = Crepidula rostrata, C. B. Ad. Pan. Shells, pp. 235, 
320, no. 353.—(Crypta rv.) H. & A. Ad. Gen. i. 369. 
Jun. var.=Crepidula uncata, Mhe. in Zeit. f. Mal. 1847, p. 184, 
no. 34. 
=Crepidula incurva, var. P. P. C. Cat. Prov. 
Garnotia solida, Gray, Gen. Moll. B. M. p. 117. 
The very remarkable form of this species has attracted the 
attention of six celebrated naturalists, each of whom have im- 
posed upon it a separate name. The first three specific names 
are identified from the types ; the other two from the very accu- 
rate descriptions given. The irregular corrugations of C. B. Ad. 
are abnormal, as are also the three ridges of Menke. Normally, 
the shell is quite smooth, with a rather glossy epidermis ; with 
338. CREPIDULA ADUNCA, Sow. 
