MAZATLAN BIVALVES 149 



Subgenus MAEGAEITIPHOEA, Meg. 

 Megerle v. Miihlfeld, 1811.— Meleagrina, Lam. 1819. 



204. Maegaeitiphoea Mazatlanica, Hani. 



Meleagrina Mazatlanica, Hani. Rec. Shells, pi. 24, f. 40. 



No synonyms of the Pearl-oyster are given, as tlie question 

 of the specific identity of the local tj^es is not yet settled. 

 The Gulf of California used to be celebrated for its pearl 

 fishery, but it appears to have been exhausted, and very few 

 oysters have been brought of late years. The specimens from 

 S. W. Mexico appeared to belong to the Panama type, being 

 small, produced and of a purplish brown. Of this shell in 1851 

 a single vessel brought 340 tons to Liverpool (T. C. Arclier.) 

 The other local types are the silver-lipped from the Society 

 Is. and the black-lipped from Manilla. Which of these is the 

 true M. margaritifera of Lam. has not yet been settled. In 

 Sanl. Deser. Cat. are also quoted, p. 264, M. radiata from the 

 PW. Indies, and M. albina from Australia. Mr. Nuttall found 

 a pretty little species, quite distinct from the young of M. 

 margaritifera, at the Sandwich Is. Pearl-oysters are also found 

 at Madagascar, Persian Gulf, Ceylon, Swan Eiver,_&c. Very 

 few specimens were sent in the Mazatlan collection, and of 

 these only the young ones were preserved. Shell in that state 

 transverse, not produced ventrally, one valve only pierced for 

 the byssus, swollen at that part, else flat, spreading ; with 

 closely set overlapping laminse, extremely thin, produced 

 into foUations or flat spines ; inside silvery white, nacre bor- 

 dered with green, margin broad, of a light tortoisesheU colour. 

 Long. 3-55, lat. 4-05, alt. 1-27, (j^-) 

 Hah. — Mazatlan ; very rare ; L'pool Sf Havre Coll. 



Tablet 681 contains a very young valve, "05 across, of nearly 

 normal shape, known from the young of the neighbouring 

 species by the enormous size of the prismatic cells. — 682, the 

 specimen above measured. 



Genus ISOGNOMON, Klein. 



Isognomon, Klein, 1753 : — Dkr. in Moll. Guin. 

 Melina, Retz, 1788, Diss. p. 28 -.—Schmn. 1817. 

 Perna, Brug. 1792 ■.—Lam. 1801 :— (non Retz.) 

 Sutura, Meg. v. Miihff. 1811. JEiitw. p. 65. 



