26 MAZATLAN BIVALVES 



Family PA^^DOEID^. 

 Genus LYO^S'SIA, Turton. 

 Syn,. Myfciliiueria, Conr. Magdala, Leach. 



36. LYOJfSIA PICTA, Sow. 



Proc. Zool. Soc. 1834, p. 88.— ?5. M. Cat. D'Orb. Moll. p. 58. 

 no. 506. 



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



?=Auatma cuneata, G-ray, Spic. Zool. vi. 1828. 



One perfect specimen of this remarkable sliell was found by 

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

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

 Gi-asti'ochfena, and disjjlays a large ossicle within. The lunular 

 portion is deeply excavated, and the posterior very greatly 

 Ijroduced. Epidermis rugose, occasionally displa3'ing 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. 12, alt. 'ftl. 



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

 microscopic structui-e, described by Dr. W. B. Carpenter in 

 JEtep. Br. Assoc. 1817, p. 105. 



Sab. — ^Attached to particles of sand in 11 fm., Isl. Muerte. 

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

 nestling in Chanite, &c., extremely rare : L'pool Col. — ':" Arica. 

 (Peru.) D'Orhigny. — The South Temperate analogue appears 

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

 TJOvh. — The W. Indian analogue is L. plicata. Gray. 



Tablet 81 contams a perfect young specimen, just beginning 

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

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

 specimen, made bj' Master John Jackson. 



Another species of Lyousia, allied to A. cuneata, Grray, has 

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

 the L'i)oolCol., 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. 



