248 

 Genus PLETHOMYTILUS. Hall. 



[Ety. : Fletho, to be full ; mytilus, a genus.] 

 (1884 : Pal. X. Y., Vol. V., Pt. I., p. 14.) 



Shell with equal gibbous valves, of an outline resembling 

 Mytilus. and haviug a finely striated ligamental area, which 

 extends across the shorter or transverse diameter of the 

 valve. Height greatly exceed ing the length. The posterior 

 side is slightly winged. Small, oblique, lateral teeth are 

 present, but no cardinal teeth have been observed. Test 

 with concentric striae. 



Plethomytilis ovifokmis. (Conrad.) ( Fig. 163.) (Pal. 

 N. Y., Vol. Y., Pt. I., p. 255, Pis. XXXI.. LXXXVII. | 



Distinguishing Characters. — Large size; ovate outline; 

 beaks projecting above the cardinal line: truncate front, 



Kir;. 1»>3. Blethomytilus oviformis. Left valve, showing striated hinge area; right 

 valve, with attenuated beak (from Hall). 



with small fissure for the passage of the byssus; widelig;i- 

 mental ;n-ea. 



Found only in the upper part of the Encrinal limestone, at 

 the lower end of Section 5 (common). 



