26 MAZATLAN BIVALVES 



FAMILY PANDOBIDJE. 

 GENUS LYOJSTSIA, Turton. 

 Syu. Mytilimeria, Conr. Magdala, Leach. 



36. LYONSIA PICTA, Sow. 



Proc. Zool. Soc. 1834, p. 88. ? B. M. Cat. D'Orb. Moll. p. 58, 



no. 506. 



? = L. cuneata, D'Orb.B. M. Cat. loc. cit. 

 ?=Anatina cuneata, Gray, Spic. Zool. vi. 1828. 



One perfect specimen of this remarkable shell was found by 

 Master F. Archer, "burrowing" [? nestling] in Spondylus, and 

 now graces his father's collection. It gapes almost as much as 

 GastrochsBna, and displays a large ossicle within. The lunular 

 portion is deeply excavated, and the posterior very greatly 

 produced. Epidermis rugose, occasionally displaying fine radi- 

 ating ridges. The growth is irregular, as usual in nestlers. The 

 amount of gape varies considerably in Mr. Cuming's specimens. 

 Size of Mr. Archer's specimen : long. *8, lat. 1'2, alt. '64. 



The few fragments I found are known at once by the peculiar 

 microscopic structure, described by Dr. W. B. Carpenter in 

 Rep. Br. Assoc. 1847, p. 105. 



Hob. Attached to particles of sand in 11 fin., Isl. Muerte, 



Cuming. Vancouver's Island, Col. Cuming. Mazatlan : 



nestling in Chamse, &c., extremely rare : IS pool Col. ? Arica, 



(Peru,) IfOrbigny. The South Temperate analogue appears 



to be L. Patagonica, "Northern Patagonia, San Bias," 



Z>' Orb. The W. Indian analogue is L. plicata, Gray. 



Tablet 84 contains a perfect young specimen, just beginning 



its gape, and displaying the radiating strise ; also a fragment of 



an older one, shewing the hinge. 85, drawings of Mr. Archer's 



specimen, made by Master John Jackson. 



Another species of Lyonsia, allied to A. cuneata, Gray, has 

 been brought from Mazatlan : but as all the fragments even, in 

 the L'poolCoL, clearly belonged to L. picta, I have not ventured 

 to include it. Like L. picta, it varies extremely in shape and 

 gape : the latter being generally small, sometimes wanting. 

 Texture smooth, extremely thin, white, glossy. 



