MAZATLAN UNIVALVES 263 
Hab.—Mazatlan ; rare, in worm-eaten passages and burrows 
of Spondylus and Chama; L’pool Col. 
Tablet 1313 contains the fry inside an adult, the nuclear 
shell, and 2 sp. in the first stage of normal growth.—13]A, a 
series of 8 sp. of different ages and patterns. One has its 
mouth filled with most beautiful spicule of sponge.—1315, a 
sp. in situ in a fragment of Spondylus. 
Faminy CALYPTRAMI1D Al. 
The genera of this family, united by Lesson, Broderip and 
Deshayes, though very different when adult in their principal 
forms, are so closely related when young that if the fry be 
examined when just emerging from the spiral nucleus it would 
be difficult to say into which genus each shell would develop. 
The ordinary young state of Crucibulum has only half a cup. 
each side being laterally adherent, resembling on the one hand 
the sunken Crepidule, as C. adunca, on the other, (supposing 
the half-cup to grow forward separate) Calyptrea proper. 
(C. equestris, &c.) The amount of lateral adherence, the 
absence of which forms the subgenus Calyptrea a of Brod., 
(C. rudis, Brod.=umbrella, Desh.) varies in specimens of the 
same species. ‘The internal lamina, more or less spread out or 
lobed in species of Crepidula, with the margins doubled 
together forming 2 cup in Crucibulum, is in Galerus very 
slightly turned over and flattened, these characters varying in 
the species. ‘Trochita is simply an extreme of Galerus on the 
one hand, or of the spiral Crepidule on the other. For par- 
ticulars of the generic synomyms, v. Gray's Synopsis in Proc. 
Zool. Soc. 1847, p. 157; H. & A. Ad. Gen. vol. i. p. 363; Phil. 
Handb. Conch. p. 186. For particulars of species, v. Brod. in 
Proc. Zool. Soc. 1834, p. 35; id. Trans. Zool. Soc. ; Desh. in 
Lam. An. s. Vert. vol. vii. p. 619; C. B. Ad. Pan. Shells, 
p. 219; B. WM. Cat. D’ Orb. Moil. p. 47. Menke’s species, given 
in Zeit. f. Mal. 1846—1851, are not described with sufficient 
accuracy to allow of certain allocation. They seem often 
named from worn and young specimens, and would probably 
have received great revision, had the author examined a large 
series of specimens like the present. As he is describing 
Mazatlan and not New Zealand shells (as his names would 
sometimes imply), his species are here allotted acording to 
the preponderance of characters. The following genera are 
