. ASTARTIDZ. 231 
the margins, thin in the middle, on the surface concentrically stri- 
ated or lamellated ; ligament external, very long; muscular impres- 
sions rather large, the anterior close to the hinge and witha 
small superimposed impression; pallial line entire, hinge un- 
known. A. intrepida, Dana (cxxii, 14). Carb.; N. S. Wales. 
This group is based upon a number of carboniferous species 
from New South Wales; they greatly resemble in external form 
the subgenus Caryatis of Cytherea, but the long ligament and 
muscular impressions appear to be very similar to those of 
Astarte. The examination of the hinge-teeth is required for the 
correct determination of the family to which these shells belong. 
Mecynopon, Keferstein, 1857. 
Distr.—Devon.; Eur. WM. carinatus, Goldfuss (exxii, 42, 43). 
Shell rather long, thin, concentrically striated or smooth, with 
a diagonal keel, extending from the beak to the posterior margin; 
ligament external, short ; hinge in either valve with an elevated, 
long tooth parallel with the hinge-margin, and a pit, posterior 
to the tooth in the right valve, and anterior to it in the left, in 
both valves a long and stout posterior lateral tooth; anterior 
muscular impression deep, with a smaller but deeper impression 
of the foot-retractor behind it; posterior impression near the 
middle of the posterior margin. 
SuspraMity CARDITINA. 
Shells roundly ovate or transversely elongated, always pro- 
vided with radiating ribs or strie. 
Carpita, Bruguiére, 1789. 
Etym.—Cardia, the heart. 
Syn.—Arcinella, Oken. Pseudocardia, Vetocardia, Conrad. 
Actinobolus, Klein, 1753. 
Distr.—50 sp. Universal. Fossil, 5 sp. Lower Silurian— 
Trias; United States, Europe, New South Wales, Tasmania. (. 
sulcata, Lam. (exxiil, 67). C. antiquata, Linn. (cexxiii, 68). 
Shell oblong, radiately ribbed; ligament external; margins 
toothed ; hinge-teeth 1:2, and an elongated posterior tooth; 
pallial line simple; anterior pedal scar close to adductor. 
Animal with the mantle-lobes free,except between the siphonal 
orifices ; branchial margin with conspicuous cirri; foot rounded 
and grooved, spinning a byssus; labial palpi short, triangular, 
plaited ; gills rounded in front, tapering behind, and united 
together, the outer pair narrowest. 
REDONIA, Rouault. Shell oval, tumid; hinge with cardinal 
and posterior teeth; anterior adductor bounded by a ridge. 
Fossil. Lower Silurian; Brittany, Portugal. C. Deshayesiana, 
Rouault (exxii, 47, 48). 
