MAZATLAN UNIVALVES 263 



^a6.— Mazatlan ; rare, in worm-eaten passages and burrows 



of Spondylus and Cliama ; L'pool Col. 



Tablet 1313 contains the fry inside an adult, 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 ita 

 mouth fiUed with most beautiful spiculis of sponge.— 1315, a 

 sp. iu situ in a fragment of Spondylus. 



Family CALYPTEiElD^: 



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 iuto which genus each sheU would develop. 

 The ordiuaiy young state of Crucibulum has only half a cup, 

 each side being laterally adherent, resembling on the one hand 

 the sunken Crepidula-, as C. adimca, on the other, (supposing 

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

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

 absence of which forms the subgenus Calj^ptrsea a of Brod., 

 (C. rudis, 5>'of?.= 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 Crucibidum, is in Galerus , very 

 sUghtly 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 Crepidula; on the other. For par- 

 ticulars of the generic svnomyms, v. Gray's Synopsis in Proc. 

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

 Handh. Condi, p. 186. For particulars of species, v. Prod, in 

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

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

 p. 219 ; B. M. Cat. B'Orh. Moll. p. 47. Menke'3 species, given 

 in Zeit. f. Mai. 1846 — 1851, are not described with sufficient 

 acCTiracy 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 ho is describing 

 Mazatlan and not New Zealand shells (as his iiames would 

 sometimes imply), his species are here allotted acording to 

 the preponderance of characters* The following genera are 



