ACEPHALA. 427 
green, and on the whole the shell is more dense and larger. One 
Specimen is more elongated than the others, and the dorsal outline is 
somewhat angular at each extremity. 
Figures 527, 527 a, lateral and dorsal views of the shell; 527 4, the 
hinge. 
CYRENA DEBILIS (Gould). 
T. parva, tenuis, transverse ovata, postice ampliata et subtruncata, sub- 
equilateralis, concentricé liris confertis, sub-reflexis arata; epidermide 
nitido, superné olivaceo induta; apicibus parum elevatis, erosis, 
absque lunula: intus violaceo-albida ; dentibus cardinalibus inconspi- 
cuts ; dentibus laterahbus elongatts, striatis. 
Cyrena debilis, Goutp; Proceed. Boston Soc. Nat. Hist., iii. 293. 
Nov. 1850. Expedition Shells, 86. 
SHELL small, thin, transversely ovate, pale yellowish-green, darker 
towards the apex, polished and shining, furrowed with fine, concentric, 
slightly reflexed ridges. Beaks not very prominent, eroded, nearly 
central, without an areola in front; anterior side a little narrowed, 
posterior extremity slightly truncated. Interior violaceous-white. 
Cardinal teeth minute; lateral teeth elongated, finely pectinate. 
Length six-tenths of an inch; height four-tenths of an inch; breadth 
one-fourth of an inch. 
Inhabits New Holland, Upper Hunter River. This locality may 
possibly be erroneous, from an accidental mixture of specimens. 
Most like C. pusilla, but has no areola in front of the beaks, and is 
less orbicular and somewhat larger. It has the aspect of a Cyclas. 
One small specimen is deep violaceous within, with four white radia- - 
tions. 
Figures 529, 529 a, lateral and dorsal views of the shell; 5294, the 
hinge. 
