MAZATLAN BIVALVES 21 



Smallest specimen, long. '018, lat. *03, alt. '015, 



Largest '13, '21, '12. 



Hab Mazatlan ; a small colony were found nestled, and 



greatly incommoding each other, in empty Balani on Murex 



princeps : Havre Col. 



Tablet 73 contains 1 specimen in situ, in Balanus ; 3 others 

 of different ages. 



29. RUPELLAEIA , sp. ind. 



Tablet 74 contains a fragment resembling R. foliacea, Desl. 

 Mazatlan ; with strong radiating ribs crossed by erect and beau- 

 tifully undulated laminae. The sculpture smoothes off at the 

 hinge margin. 

 Hob. Mazatlan ; from the back of a Spondylus Lamarokii ; 



ISpool Col. 



FAMILY COEBULIB^. 

 GENUS COKBULA, Brug. 



30. COKBULA BICARINATA, Soiv. 



Proc. Zool. Soc. 1833, p. 35. Mull. Syn. Test. Viv. p. 229. 



Rve. Conch. Ic. 1844, pi. 3. f. 23. Hani, in Wood's Suppl. 



Ind. Test. pi. 12, f. 31. Hani. Descr. Cat. p. 46. B. M. C<ft. 



D'Orb. Moll. p. 70, no. 619. 



Shell extremely swollen, the valves nearly equal, sometimes 

 one a little overlapping the other at the posterior ventral margin . 

 Epidermis thin over the body, thick over the margins of the 

 valves. Irregularly concentrically striated over the surface, 

 very finely between the posterior keels : umbonal portion 

 smooth. Within, ligament affixed to the smaller tooth : pos- 

 terior muscular scar rounded, on a projecting support ; a 

 smaller one behind : anterior scar oblong. Pallial line simple. 

 In the 3 specimens which alone I have had an opportunity of 

 examining, which are quite fresh, I cannot detect any pallial 

 sinus. Those who have plenty of Corbula3 would do well to 

 examine their interiors, which are not generally noticed in the 

 -descriptions. They are either very rare at Mazatlan, or have 

 escaped detection, scarcely a dozen specimens having been 

 found of all the species. Long. 2' 7, lat. "36, alt. '28. 

 Hab. In. sandy mud, 717 fm., Panama, Eeal Llejos, Caraccas, 



St. Elena, Cuming.West Columbia, Hanley, Jay. Ecuador, 



