SPONDYLIDA. 285 
strongly impressed grooves to receive the dental processes of 
the other valve. Fossil, 16 sp. Lias and Lower Oolite; 
France and England. 
SponDyLus (Pliny), Linn. 
Thorny-oyster. 
Syn.—Dianchora, Sby.,1814. Podopsis, Lam.,1819. Pachytes, 
Defr., 1825. (All based upon casts or imperfect specimens.— 
DESHAYES. ) 
Distr.—68 sp. West Indies, Canaries, Mediterranean, India, 
Torres Straits, Pacific, West America; 105 fathoms. Fossil, 
80 sp. Carb—; Europe, United States, India. 8S. regius, Linn. 
(exxxi, 71, 73). S. Americanus, Lam. (exxxi, 72). 
Shell irregular, attached by the right valve, radiately ribbed, 
spiny or foliaceous; umbones remote, eared; lower valve with 
a triangular hinge-area, cartilage in a central groove, nearly or 
quite covered ; hinge of two curved interlocking teeth in each 
valve; adductor impression double. 
Animal with the mantle open and gills separate, as in 
Pecten; lips foliaceous, palpi short; foot small, cylindrical, 
truncated. 
In aged specimens the circular portion of the muscular scar 
exhibits dendritic vascular markings. The lower valve is always 
most spiny and least colored ; in some species (like S. ¢mperialis) 
the shell is scarcely, if at all, attached by its beak or spines. 
The inner shell-layer is very distinct from the outer, and always 
wanting in fossil specimens from calcareous rocks, then called 
Dianchore. Specimens from the Miocene of St. Domingo, 
which have lost this layer, contain a loose mould of the original 
interior. Water-cavities are common in the inner layer, the 
border of the mantle having deposited shell more rapidly than 
the umbonal portion. 
Prepum, Brug., 1792. 
Distr.—Red Sea, Indian Ocean, Mauritius, Chinese Seas. P. 
Spondyloideum, Gmel. (cxxxi, 70). 
Shell thin, smooth, compressed, attached by a byssus passing 
through a deep notch in the right valve. Inhabits coral-reefs, 
where. it is found half-embedded. 
TERQUEMIA, ae 1867. 
Etym.—Dedicated to M. O. Terquem, an eminent palon- 
tologist. 
Syn.—Carpenteria, E. Deslongchamps, 1858 (non Gray, 1856). 
Distr.—Fossil, 5 sp. Trias—Lias; France, Germany, Great 
Britain. 7. Heberti, Terquem. 
Shell inequivalve, subequilateral, attached by the umbonal 
portion of the right valve; the left valve slightly concave 
