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Super family Pteriacea. 

 Family Pinnidae. 



C-en\xs ^I"T'^A (linnaeus) lamarclc. 



PIIIIJA HE?U?;OA n. sp. 



Desori'Qtion ,- '^hell small, slender, moderately thicic, 

 strongly convex; summit of the shell subangular to roiir.ded, sit- 

 uated nearer the dorsal margin; 'dorsal surface almost flat, the 

 ventral gently arcuate; a^pex rounded; dorsal and ventral margins 

 straight, diver?-ing at an angle of about 25°; external surface 

 with a well-definec'., relatively deep sulcus, beginning near the 

 anterior end and extending posteriorly along the sumniit of the 

 shell; dorsal region of the shell sculptured with :^lve well-de- 

 lined longitudinal rid^^;^, excluding the ridge adjacent to the 

 sulcus; upper half or more of the ventral portion sculptured with 

 three more irregular, broader, lower ridges, followed (toward 

 the ventral margin) by oblinue, obscure iindulations, diverging 

 slightly from the margin and terminating abruptly at the longi- 

 tudinal rid'-es; inner surface v;ith a lov7, narrow ridge corres- 

 ponding to the external auleus. 



Dimensions .- Length, about 65 ram.; max. alt., 17.5 mm.; 

 max. semidiarr.., 7.8 mm. 



