OF CONCHOLOQY. 39 



DESCRIPTIONS OF NEW SPECIES OP PHOLADIDiE. 



BY GEORGE W. TRYON, JR. 

 NAVEA, Gray. 



1. N. Newcombii, Tryon. — pi. 2, f. 1, 2, 3. 



Description. — Shell subglobose, obtusely rounded posteriorly, 

 diagonally truncate anteriorly, the sinus formed by the two 

 valves broadly cordate, exhibiting the interior. Surface di- 

 vided in the centre by an impressed line from the beaks to 

 the basal margiu. The margin of the valve posterior to this 

 line is almost regularly semicircular, and devoid of stria?, ex- 

 cept the growth marks. Anterior to the line the margin is 

 diagonally emarginate, and the surface is covered with crowded 

 shagrined radiating ribs. Margin of the hiatus thickened 

 internally and denticulate. Apophysis long, blade shaped, 

 curved forwards. 



Dimensions. — Length •25 inch ; width '30 inch ; Diameter 

 •25 inch. 

 Sahitat, Australia. Wesley Newcomb, M. D. 



My Cabinet, Cabinet of Dr. Newcomb. 



Observa'ions. — Three other species of Navea have been de- 

 scribed ; the N, nucivora of Spengler is longer than wide, 

 with a very small hiatus, iV. tenuis, Gray is thin, and the 

 anterior portion is only concentrically striate, instead of 

 radiately ribbed. Our species is more nearly related to iV. 

 subglohosa Gray, but that shell may be distinguished from it 

 by being longer than wide, with the hiatus nearly perpendicu- 

 lar, its margin but little curved, and by the paucity of ribs 

 anteriorly. 



PENITELLA, Valenciennes. 



2. P. PARVA, Tryon.— pi. 2, f. 4, 5. 



Description. — Shell small, ovate, inflated, rather thick. Sur- 

 flice divided by an oblique impressed rib, posteriorly to which 

 it is concentrically striate, while anteriorly it is radiately 

 ribbed. 



The reflexed dorsal margins are each covered with a thick, 

 irregularly shaped accessory valve, with a single central valve 

 posterior to them. The latter is somewhat pentagonal, emar- 

 ginate in front. 



Hiatus filled by a heavy callus, which juts out somewhat 

 into a point or beak, instead of preserving a rounded outline. 



