112 



pellucid, corneous, about eighteen radiating ribs running 

 the entire length of the shell; ventral edge rounded. 

 2L..6. S. Coasts. Towards the middle posteriorly, 

 the scaly striae run obliquely to the margin. 



* P. PAPYRACEA. Turt.B. p. 224. t. 20. /. 3. F. 

 p. 407. Oval triangular, thin, brittle, with nine dis- 

 tant unarmed ribs nearly covering the entire surface ; 

 ventral edge slightly rounded ; contracted rapidly to- 

 wards the apex ; the open end even. 2j...4i. Devon. 



TRIBE. MALLEACEA. LAM. 



Subinequivalve, foliaceous, ligament marginal; sub- 

 linear either entirely simple or interrupted by ere- 

 nulations or a row of teeth. 



GENUS. CRENATULA. 



Subequivalve, flattened, foliaceous, somewhat irregular, 

 no particular aperture for the byssus ; hinge lateral, 

 linear, marginal, crenulated ; crenations arranged 

 in a straight line, callous, somewhat excavated, re~ 

 ceiving the ligament. 

 C. TRAVISII. Turton in Mag. N. H. 7. p. 349. /. 



* Muricata, fide Turton, is probably not native. 



