134 MAZATLAN BIVALVES 



181. AECA MULTICOSTATA, Sow. 



Proc.. Zool. Soc. 1833, p. 21. Rve. Conch. Ic< pi. 4, f. 23. 

 Hani. Eec. Shells, pi. 19, f. 12. 



One very fine specimen of this shell was found by Mr. Archer. 

 It differs from A. grandis in being much lighter, with more 

 numerous ribs, and a squarer form. Long. 2 '65, lat. 3 '16, 

 alt. 2 '36. 



Hob Gulf of Tehuantepec, 12 fm., Cuming Mazatlan ; ex- 

 tremely rare ; Lpool Col. 



Tablet 628 contains a very small valve, '15 across, which 

 may belong to this species. 629, a drawing of Mr. Archer's 

 specimen. 



182. AECA PLABIATA, Sow. 



Proc. Zool. Soc. 1833, p. 21. Eve. Conch. Ic. pi. 1, f. 7. 



Hani. Descr. Cat. p. 160. .5. M. Cat. DOrb. Moll. p. 81, 



no. 720. 

 Comp. A. labiosa, Soiv. loc. cit. live. Conch. Ic. pi. 10, f. 67. 



Hani. Descr. Cat. p. 159, pi. 19, f. 3. B. M. Cat. DOrb. 



Moll. p. 81, no. 720. 

 Comp. A. incongrua, Say, Journ. Ac. Nat. Sc. Phil. vol. ii. 



p. 26$. Hani. Descr. Cat. p. 159. 



The three species above quoted are very nearly allied. The 

 two specimens found in the L'pool Col. by Messrs. Hibbert 

 and Archer, before it fell into the dealer's hands, are exactly 

 Kke the specimens brought from Florida, by J. J. Au-dubon. 

 Shell with distant beaks, and strong ligament filling up a large 

 rhomboidal area. Shape subangular ; tubercles absent from 

 the angular part, also from the front of the smaller valve. 

 Teeth rather broad. Long, (fromumbo) 1'23, lat. 1 '3, alt. 1'04. 

 Hob. Eeal Llejos and Tumbez, Peru, in sandy mud, 7 fm, 



Cuming. Mazatlan ; extremely rare ; L'pool Col. 



Tablet 630 contains a specimen, presented by J. Hibbert, Esq. 



183. AECA BIFEOXS, n. s. 



A. t. turgidd, subquadratd, tenui, maxime incequivalvi, postice 

 angulatd, umbonibus hand distantibus ; alba, epidermide I & v i , 

 olivaced indutd ; costis circiter xxx., in testa junior e omnibus 

 tuberculosis ; in adultd solum viii. x. anticis, religuis Icevibu* : 

 costis ventralibus in v alv d m in ore p arvis , rotund at is 9 



