﻿10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 59 



slightly wavy, flat teeth. Height 25 ; length of shell 25 ; of hinge- 

 line 14; max. diameter 26 mm. 



Station 5882 h. Types, U. S. Nat. Mus. 214343. 



This is one of the most abundant species in the above mentioned 

 beds, but does not appear to reach a large size. It is the precursor 

 of A. Chemnitsii Philippi, of the recent fauna. 



There are also a number of Pyramidellidse which have been sub- 

 mitted to Dr. Paul Bartsch for determination. 



PECTEN (LYROPECTEN) PITTIERI, new species 



Shell large, nearly equivalve, suborbicular, coarsely sculptured; 

 left valve moderately convex, with ten strong rounded ribs, obsolete 

 distally, with shallow rounded interspaces at first narrower, after- 

 ward wider than the ribs ; submargins wide, subequal, radially 

 sculptured with coarse, somewhat irregular threads, about ten in 

 number, which when perfect have a fine, concentric, imbricate 

 sculpture ; similar radial sculpture covers both valves, the threads 

 coarser and more regular on the right valve ; of the major ribs on 

 the left valve, five alternating ones bear on their proximal halves 

 six to ten prominent, thin, evenly spaced, vaulted scales, resembling 

 those of P. imbricatus Gmelin ; similar scales are wanting in the right 

 valve ; ears subequal, with about half a dozen radial threads and 

 dense, concentric sculpture ; margin of the valve wavy, not sulcate ; 

 interior with ten deeply channelled, wide sulci corresponding to the 

 external ribs, the angles of the interspaces emphasized near the 

 valve margin ; hinge with a deep subtriangular pit for the resilium, 

 a strong anterior ridge and two marked posterior grooves with a 

 ridge between them. Adductor scar large, with a rather ragged 

 margin. Right valve with eleven stronger ribs, each carrying five 

 or six riblets, with two or three similar riblets in the interspaces ; the 

 proximal halves of the ribs are slightlly undulated but not scaly; 

 ears subequal, rudely imbricate on the dorsal margin and on the 

 four or five radial threads of the anterior ear ; ctenolium with about 

 16 spines, byssal notch narrow, angular; hinge-line grooved recip- 

 rocally to that of the left valve. Height 132; length of shell 152; 

 of hinge-line 82 ; max. diameter omitting spines 46 mm. 



Locality, Moin Hill, near Port Limon, Costa Rica, niveau a. H. 

 Pittier, 1899. 



Type, U. S. Nat. Mus. 214368. 



This fine and remarkable species is somewhat intermediate 

 between Lyropecten and Nodipecten, and when young must have 

 the aspect of a Chlamys much like C. imbricatus. 



