MAZATLAN UNIVALVES 263 



Hob. Mazatlan ; rare, in worm-eaten passages and burrows 



of Spondylus and Chama ; L'pool Col. 



Tablet 1313 contains the fry inside an adnlt, the nuclear 

 shell, and 2 sp. in the first stage of normal growth. 1314, a 

 series of 8 sp. of different ages and patterns. One has its 

 mouth filled with most beautiful spiculse of sponge. 1315, a 

 sp. in situ in a fragment of Spondylus. 



FAMILY 



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 tne one hand 

 the sunken Crepidulse, as C. adunca, on the other, (supposing 

 the half-cup to grow forward separate) Calyptrsea proper, 

 (C. equestris, &c.) The amount of lateral adherence, the 

 absence of which forms the subgenus Calyptrsea a of JJrod., 

 (C. rudis, Brod. = umbrella, Desk.) 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 a 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 Crepidulse on the other. For par- 

 ticulars of the generic synomyms, v. Grays Synopsis in Proc. 

 Zool. Soc. 1847, p. 157 ; H. # A. Ad. Gen. vol. i. p. 363 ; Phil. 

 j&andb. ConcJi. p. 186. For particulars of species, v. Brod. in 

 Proc. Zool. Soc. 1834, p. 35 ; id. Trans. Zool. Soc. ; Desk, in 

 Lam. An. s. Vert. vol. vii. p. 619 ; C. B. Ad. Pan. Shells, 

 p. 219 ; B. M. Cat. D'Orl. Moll. p. 47. Menke's species, given 

 in Zeit. f. Mai. 18461851, are not described with sufficient 

 accuracy to allow gf certain allocation. They seem often 

 named from worn and young specimens, and would probably 

 have received great revision, had the author examined a la^ge 

 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 



