196 VERTICORDIIDA. 
valves. Fossil. Eocene; France. JL. aviculare, Lam. (exvii, 1). 
These shells present considerable resemblance to Tridacna. 
GOLDFUSSIA, Castelnau, 1843, is based upon Cardium nautiloides, 
each valve of which is said to resemble a laterally compressed 
nautilus, keeled on either side. Silurian; South America. 
? DextopraA, Winchell, 1863. 
Distr.—Devon., Carb.; U. 8. D. ovata, Hall. 
Shell thin, inequivalve, inequilateral; beaks separated by an 
undefined area; right valve very ventricose, with a very promi- 
nent umbo, and a produced, incurved beak strongly inclined 
forward; left valve much less inflated, with a less prominent 
beak, scarcely elevated above the dorsal margin; hinge-line 
more or less extended, straight or slightly bent, edentulous ? 
furnished with a thickened cartilage-plate bearing a lineal pos- 
terior groove; pallial line and muscular markings unknown. 
Carpropsis, Meek and Worthen, 1861. 
Distr.—Several paleeozoic species; U.S. C. radiata, M.and W. 
(exvi; 95). 
Sheil equivalve, somewhat inequilateral, very slightly oblique, 
ovate or cordiform, entirely closed; beaks rather elevated, 
distinctly incurved, and directed towards the anterior side ; 
surface marked by radiating strie or cost ; cardinal margin 
short, and rounding into the posterior border; hinge provided 
with one or two distinct anterior teeth in each valve, near the 
beaks (ligament and muscular impressions unknown). 
ByssocarpruM, Munier-Chalmas, 1882. 
Distr.—2 sp. Eocene and Miocene; France. £B. emargin- 
atum, Desh. 
Shell allied to Lithocardium, but characterized by an anterior 
opening fora large byssus, having margins toothed like those of 
a Tridacna; anterior muscular impression very feeble, placed 
below the posterior cardinal tooth. 
Famity VERTICORDIID 2. 
Shell equivalve, or nearly so, of small size, inflated, with the 
beaks incurved, closed all round, more or less solid, pearly 
inside; hinge with few cardinal teeth, more or less obsolete, 
ligament subinternal or internal; two muscular impressions, 
pallial line simple. 
The animal of V. Japonica has the mantle-margins united, 
with a small anterior opening for the protrusion of the foot, 
which is small, triangular, compressed, and a posterior roundish, 
fringed opening in which are inclosed two separated but very 
short siphons; labial palps small. 
