72 MAZATLAN BIVALVES 



into a tube. The epidermis is extremely thin, but important 

 to preserve the shell, which soon becomes of a calcined appear- 

 ance without it. The radiating striae become obsolete in the old 

 shells, but not so much so as in Ch. amathusia. The smallest 

 valve measures *03 in length : the largest specimen, long. 3*5, 

 lot. 3 '56, alt. (without spines) 2*3. 



Hob. Payta, Peru, Fontaine, D'Orbigny. Panama, rare, C. B. 

 Adams. San Bias, Jay. Mazatlan ; Lieut. G-reen, (Gould 

 ms.) ; extremely abundant ; I! pool fy Havre Coll. 

 Tablet 319 contains 3 very young valves. 320, 4 young 

 specimens, form somewhat rounded. 321, 3 do. adolescent. 

 322, 3 do. adult. 323, 3 young, slightly produced 324, 3 do. 

 adolescent. 325, 2 do. adult, ribs close. 326, 3 do. young, 

 more produced. 327, 2 do. adult. 328, 4 young, rather flat- 

 tened, with distant laminae. 329, 3 do. adolescent. 330, 2 do. 

 adult. 331, 5 young specimens set to shew the ventral margin 

 in different stages of growth. 332, 4 do. adolescent. 333, 4 do. 

 adult. 334, 2 sp. shewing the nearest approach to Ch. amathusia, 

 and unnatural longitudinal grooves. 335, 1 sp., ribs not foli- 

 ated ventrally. 336, 2 do., ribs flattened. 337, 1 do., strongly 

 foliaceous. 338, 1 do., foliations semispinous. 339, 1 sp. de- 

 formed growth. 340, 3 do. with irregular ribs. In all 59 

 specimens. 



102. VENUS (CHIONE) AMATHUSIA, Phil, 



Venus amathusia, Phil. AbUld. p. 129, pi. 2, f. 4. C. B. Ad. 



Pan. Shells, p. 269, no. 435. Sow. Thes. Conch, p. 709, 



pi. 154, f. 26, 27. 



Chione gnidia, var. Desk. B. M. Cat. Yen. p. 133, no. 41. 

 + Chione amathusia, Desh. do. p. 132, no. 39. 

 ?= Venus cancellata, MenJce in Zeit.f. Mai. 1847, p. 191, no. 



58, (non Lam.) 

 ?= Venus succincta, Vol. in Humb. Rec. d'Obs. vol. ii. 



I follow Hani. Sow. and ? C. B. Ad. in regarding this as 

 Philippi's species. It agrees exactly with the description ; not 

 with the figure. I have however a very worn young stumpy 

 specimen from S. W. Mexico, which is sufficiently like the 

 figure, especially when it is remembered that figures are not 

 always like the shell. I cannot say that I should have known 

 it even from Sow.'s figure, which is much better. Desh. re- 

 gards Phil.'s species as distinct, and (with Dr. Gray) considers 

 this a variety of Ch. gnidia. What changes the creatures make 



