400 MOLLUSCA. 
equal, radiating strice, and when examined by a magnifier, the whole 
surface is found to have minute, undulating strie. There is a very 
conspicuous Tellina-like fold posteriorly ; the anterior end is a little 
the longer, somewhat less elevated than the posterior, which is a little 
truncated and slightly gaping. Beaks prominent, pointed, conti- 
guous, with a small, lanceolate pit in front. Interior of a beautiful 
saffron tint; the portion to which the mantle adheres having a dead 
surface, marked with scattered, shining dots. Hinge very strong; 
ligament pit large and deep; teeth beautifully and deeply tinted rose- 
red. 
Length three and a half inches; height three and a quarter inches ; 
breadth one and a quarter inches. 
Inhabits Callao. (?) 
Very distinct from all other described species, unless it may be A. 
solidum, Gray. From comparison with his description alone, this must 
be different. 
Figures 512, 5124, exterior and interior of the shell. 
MeESoDESMA MUNDUM (Gould). 
T. parva, solidula, convextuscula, ovato-triangularis, levis, epidermide 
stramineo induta ; natibus post-medianis, acutis ; margine dorsal viz 
arcuato, postice subito dechivi; latere antico angustato, acuto ; latere 
postico rotundato ; margine ventrali valde arcuato: interior flavescens, 
cicatricibus impressts: cardo dentibus validis instructus. 
Mesodesma munda, Goutp ; Proceed. Boston Soc. Nat. Hist., 111. 217. 
May 1850. Expedition Shells, 77. 
SuHeLL solid, smooth, cream-coloured, imequilateral, compressed, 
ovate-trigonal, cuneiform, transverse; beaks elevated, acute, at the 
posterior third, forming a right angle; posterior extremity broadly 
rounded ; anterior end subtriangular, acutely rounded, point below the 
middle; ventral margin regularly curved; anterior dorsal margin 
rectilinear. Interior yellowish-white; muscular impressions deep. 
Teeth well-developed, like M. strata. 
