MANUAL OF THE MOLLUSCA. 
IsopomA, Deshayes, 1860. 
Type, 1. cyrenoides, Deshayes. Hocene. Paris basin. 
Shell transversely oval, very thin; hinge similar to that of 
Cyrena, but the pallial line is sinuous. 
Famity XVI.—TELLINIDA.* 
SowERBYA, D’Orbigny, 1850 (see p. 478). 
Dedicated to Sowerby, author of ‘‘ British Mineral Con- 
chology,” &ec. 
Type, S. crassa, D’Orb., Prodrome L., p. 362. 
Synonym, Isodonta,.Buvignier, 1851. | 
Shell equivalve, subequilateral ; right valve with two oblique, 
diverging, cardinal teeth separated by a mesial trigonal socket, 
and two lamellar lateral teeth separated from the hinge border 
by longitudinal grooves; left valve with a conical tooth between 
two oblique pits; laterals two; longitudinal lamellar and pro- 
jecting, and united to the superior border; ligament external. 
Fossil, 8 species. Lower Lias—Portlandian. England, 
France, Germany. 
QUENSTEDTIA, Morris and Lycett, 1853 (see p. 481). 
Dedicated to Professor Quenstedt, the veteran palzeontologist 
of Wurtemberg. 
Type, Pullastra oblita, Phillips. 
Shell like that of Psammobia ; hinge with an obtuse transverse 
cardinal tooth in the left, and a cardinal pit in the right; liga- 
ment external, in a narrow elongated groove ; posterior adductor 
scar rounded, anterior elongated, sinuated; pallial sinus smaller 
than in Psammobia or Sanguinolaria. 
Fossil, 3 species. Inferior Oolte—Great Oolite. England, 
France, Germany. 
P PALmMomYA, Zittel, 1861. 
Shell triangular, depressed, nearly equivalve, inequilateral ; 
right valve with two cardinal teeth, the posterior larger and in 
front of the cartilage pit; left valve with a single cardinal 
tooth; a prominent posterior lateral tooth in each valve; 
muscular and pallial impressions very faint. 
Fossil, 1 species. Coral Rag. Glos, Normandy. 
# See p. 479, 
78 
