MAZATLAN BIVALVES 73 



in other places I do not know, except from tlie picked spG#B-- 

 mens in Mr. Cuming's Col. He regards the species as distinct. 

 The Mazatlan shells would never have encouraged any one to 

 unite them : neither Collector nor dealers offered to put them 

 together. I have very narrowly examined about 400 specimens 

 of this shell, and more than 6t)0 of Ch. gnidia, nor did I find a 

 single intermediate form. The texture of the shells varies 

 as earthenware from china ; Ch. amathusia iinder the epidermis 

 being glossy, and of a very light brownish purple ; Ch. gnidia in 

 the same circumstances having the appearance of a baked shell, 

 dull, and of a darker brown. The concentric ribs are peculiarly 

 lustrous, and are very short and stumpy, rarely shewing any 

 tendency to rise into scales. The radiating strise are very 

 much famter, shewing a disposition to gather in twos in the 

 yoiuig shell. The lunular portion is much larger, smoother, 

 and of a richer purple. Both species within shew the middle 

 teeth slightly furcate, the pallial line distant from the margin, 

 and the sinus small. Ch. amathusia is generally smaller, more 

 swollen, with a thicker shell and margin ; and is more angula- 

 ted posteriorly. It is represented by Ch. caucellata in the 

 Caribbsean sea, and its yoving may be the shell so named in 

 Menke's Mazatlan list. The smallest specimen found is 1'5 

 w?. long ; the largest measures long. 2 '43, lat. 2 '74, alt. l'6o. 



Hab. — ? Panama, very rare, C. B. Adams. — S. W. Mexico, 

 P. P. C. — Mazatlan; Lieut. Green, (Gould ms.)— Do. ;. com- 

 mon and very fine ; L'p'mjI ^ Havre Coll. 



Tablet 341 contains 3 specimens, rounded form. — 342, 3 do. 

 more angulated. — 343, 3 do. close ribs. — 344, 3 do. produced 

 posteriorly. — 345, 3 do. distant ribs. — 346, 3 do. swoUen form. — 

 :M<7, 3 do. produced.— 348, 3 do. even growth.— 349, 1 do. witli 

 irregular ribs. In all 25 specimens. 



103. Venus (? Chione) , si?. ind. 



This can scarcely be the young of Cli. amathusia, since the 

 s] lap e is very different, being su1 (quadrate. Surface more or 

 less distinctly marked with fine concentric ridges and radiating 

 striffi, sometimes nearly smootli ; lunide clearly marked ; an- 

 terior tooth rather long ; iiaUial line distant from margin ; 

 sinus broad, shallow. Colour innk or light green. The largest 

 specimen measures long. '09, lat. "12, alt. '06. 



Oct. 1855. h 



