382 AXEL A. OLSSON 



merely bevelled or bladelike at these points so as to fit into the lateral 

 sockets in the opposite valve. The pallial sinus is large, high, and irregularly 

 rounded under the beaks, almost reaching to the anterior adductor scar, and 

 wholly confluent with the pallial hne below. 



Merisca crystallina (Spengler) Plate 70, f.gures 2, 2a 



Telllna crystallina Spengler, 1798, Skr. Nat. Selsk. (Copenhagen), vol. 4, No. 2, p. 113 



refers to Chemnitz, 1795, Neues Syst. Conchyl.-Cab. Martini-Chemnitz, bd. 11, 



p. 210, pi. 199, figs. 1947, 1948.— Hanley, 1846, Thes. Conch., vol. 1, Tellina, p. 



270, No. 89, pi. 5/, fig. 43. 

 Tellina (Merisca) crystallina Wood, Dall, 1900, Proc. U.S. Nat. Museum, vol. 23, No. 



1210, pp. 293, 302, 311, pi. 2, fig. 10.— Maxwell Smith, 1944, Panamic Marine 



Shells, p. 64, fig. 834. 

 Tellina {Merisca) crystallina Spengler, Hertlein and Strong, 1949, Zoologica, vol. 34, pt. 



2, No. 9, pp. 82, 83. — Hertlein and Strong, 1955, Amsr. Mus. Nat. Hist., vol. 



107, art. 2, pp. 198, 199. in part. 



Shell roundly trigonal, relatively thin, white, or translucent, inequivalve, 

 the left valve Is larger, more convex than the left which is strongly flattened 

 or depressed; the posterior side in both valves is strongly and narrowly flexed 

 ending at its tip in a pronounced snoutlike end. The valves are inequilateral, 

 the ventral margin is widely rounded, forming almost a half circle, the small, 

 sharply angled beaks placed near the middle, dorsal margins on both sides 

 long and perfectly straight. Surface sculpture is formed by thin, lamellar, 

 concentric riblets, spaced about a millimeter apart, their wide interspaces 

 marked with minute growth lines. 



Length 25.7 mm., height 18.8 mm., diameter of both valves G.7 mm. 

 Monte Cristi, Dominican Republic. 



Merisca crystallina, typically a Caribbean and West Atlantic species, 

 has been reported frequently from the Panamic-Pacific region. Hertlein and 

 Strong discussed this species at some length and reached the conclusion that 

 the specimen figured by Chemnitz represented the Caribbean shell and that 

 it likely came from the Danish West Indies, then a Danish possession. Dall, 

 followed later by Hertlein and Strong, considered the species as also Pacific. 

 As here understood, typical M. crystallina is a thin, trigonal shell, with nearly 

 median beaks, and the dorsal margin on both sides of the beak is long and 

 straight, its sculpture uniform and coarse. Figures of a specimen from the 

 Dominican Republic for more ready comparison with the Pacific forms are 

 shown on the plate. 



Range — South Carolina southward to the Carribbean. Also fossil in Mio- 

 cene and Pliocene rocks. 



Merisca rhjnchoscuta, new species Plate 70, figures 3-3b 



Shell with the upper half of each valve trigonal, the beaks elevated and 

 sharp, pointed forward, the lower or ventral half widely rounded and forming 

 a half circle. The left valve Is moderately convex, the right flattened or 

 depressed, each with Its posterior side produced at the end into a short but 

 conspicuous snout flexed towards the light. Color white or glassy, sculptured 

 with strong, concentric ridges or lamellae usually spaced 1 to 11/4 mm. apart, 

 the Interspaces between them flattened and marked with small lines of 

 growth. 



Length 24.6 mm., height 17.8 mm., diameter 3 mm. (right valve), 

 Manglaralto, Ecuador. Holotype, ANSP 218942. 



