MAZATLAN UNIVALVES 507 



stones near low water mark, rare ; C. B. Adams. Mazatlan ; 

 very rare ; L'pool Col. 



Tablet 2419 contains 3 sp. narrow. 2420, 3 do. broader. 

 2421, 2 sp. one with operculum, the other after the acid process. 



j. 646, (b.J ANACHIS (? COSTELLATA, var.) PACHYDEEMA. 



A. t. "A. costellata" simillimd, sed plerumque latiore, fusco- 

 purpured, albido fasciatd et in tuberculis maculatd ; epidermide 

 solidd, rugis incrementi confertis ornatd, Jiaud valde adhcerente ; 

 operculo elongato, subarcuato, scabriusculo, apice terminali 

 scepe decollate. 



Corap. Columbella varia, Sow. in Proc. Zool. Soc. 1832, p. 116. 

 Mull. Syn. Nov. Test. Viv. p. 86. Sow. TJies. Conch, p. 130, 

 no. 54, pi. 39, f. 116-7. Desk, in Lam. An. s. Vert. vol. x. 

 p. 282, no. 31. C. B. Ad. Pan. Shells, p. 100, no. 105. 

 = (Colnmbella) Anachis varia, H. Sf A. Ad. Gen. i. 184. 

 It might be thought that the true A. costellata is this shell 

 with the outer part of the epidermis rubbed off ; but in this 

 form, when the epidermis comes off, it leaves the dark purplish 

 brown surface of the shell itself, not the close thin skin of the 

 chesnut-stained A. costellata. These shells were regarded by 

 an eminent authority as one of the many varieties of A. varia.* 

 They appear however much more nearly related to A. costel- 

 lata, from which the operculum does not perceptibly differ. 

 This shell, like A. costellata, is more or less turrited, sometimes 

 obese ; with ribs more or less numerous, more or less waved, 

 more or less produced towards the base ; interstices more or 

 less cancellated by spiral striae. The flattening of the middle 

 of the lip often gives the ribs the appearance of being slightly 

 tubercular both above and below. Colour purple brown, 

 more or less dark and spotted or banded with white. The 

 best character is the epidermis, which is thick, lying in trans- 

 verse layers as in C. major, but coarser in proportion, dark 

 green. A broad sp. measures long. '66, long. spir. "34, lot. '32, 

 div. 40. 



Hab Mazatlan ; rare ; L'pool Col. 



Tablet 2422 contains 6 sp. in different stages. 2423, 1 sp. 

 with operculum in situ, and one separate operculum. 



* The Col. terpsichore of Menke may belong to this species, though his 

 diagnosis appears to apply better to C. coronata. 



