Philobri/ft.] PELECYPODA. 857 



a well limited and defined disc, occupying a good part of the cardinal 

 line. 



Animal viviparous. 



An account of the anatomy of P. sublcevis has been published by 

 Pelseneer in the Voyage du S.Y. " Belgica," Mollusques, 1903, 42, 

 pi. 7, f. 95 ; pi. 8. f. 96-99. 



Distribution. Cosmopolitan, from the littoral zone to about 200 

 fathoms. 



Fossil in the Secondary and Tertiary : in the Pliocene of New 

 Zealand. 



KEY TO SPECIES. 



A. Shell very distinctly costate. 



a. Shell triangular, ventricose, with 11 close and grooved costse cost/ita. 

 aa. Shell ovate, hut slightly ventricose, with 10 carinated cost* Filholi. 



B. Shell smooth or feehly costate. 



a. Shell, subquadrangular, sometimes mytiliform, with 8-12 

 faint costa? or smooth ; anterior end straight or concave, 

 not advancing . . . . . . . . . . meleagrma. 



aa. Shell pyriform, smooth or with faint radial stria' : anterior 



end advancing a little in front of the beaks . . . . modiolus. 



1. Philobrya costata, Bernard, 1896. Plate ni, tig. 13. 



Hochstetteria costata, Bernard, Bull, des Naturalistes du Museum, ii, 1896. 

 Pliilolirya coslata, Bernard, J. de Conch., xlv, 1897, 15, pi. 1, f. 5 ; 33, 

 f. 7 in text : Bernard, Rech. Ontogen. et Morphol. sur la Coq. des Lamelli- 

 branches. 1898, 115, f. 1-5 in text, 



Shell small, thick, ventricose, very inequilateral, sub quadrangular, 

 strongly radiately ribbed. Beaks close together, with a distinct flat 

 and oblique prodissoconch, inclined towards the inner and posterior 

 sides, with a sharp raised margin and slight radial striations. Anterior 

 end nearly straight, descending obliquely and forming an angle of 

 60 to 70 with the dorsal margin. Posterior end short and straight 

 or lightly excavated above, very lightly convex at the lower half ; 

 basal margin regularly curved. Lunular area large, cordiform, flat, 

 with concentric riblets. Escutcheon lightly keeled. Sculpture con- 

 sisting of 11 equidistant strong radial ribs, each with a distinct 

 median groove, the interstices near the base almost of the same width 

 as the costao ; to these riblets have to be added 3 to 4 thin simple 

 concentric cords upon the lunular area ; the interstices and riblets 

 are ornamented with close wavy and sharp concentric stripe. Epi- 

 dermis produced into double hair-like processes upon the riblets, and 

 extending beyond the margins of the valves. Colour light browu. 

 Interior light brown, with white radiate rays, corresponding to the 

 interstices on the surface. Margins denticulated by the extension of 

 the costse, and finely crenulate. Hinge-plate narrow, with a long- 

 crenellated posterior ridge ; below the anterior portion of the beak 

 there is a short subquadrangular and cancellated area with 3 roundish 

 small tubercles in front. Ligament oblique, below the posterior part 



