JT7KES-BK0WNE : CBETACEOIJS AND EOCENE VENEEID-SI. 171 



It is a fairly large shell, varying in transverse length from 32 to 

 46 mm. (i.e. up to 1|- inch). It is oval in shape, with a thick shell, 

 and a strong hinge-plate, hearing three stout widely-divergent teeth, 

 the anterior one being close under and parallel to the lunular border. 

 The pallial sinus is short and evenly rounded. The valve-margins 

 are crenulated. The surface-sculpture has the combined radial and 

 concentric elements of Chione, the concentric ribs being the more 

 conspicuous. It resembles such recent species as C. pedorina or 

 C. asperrima, except in the relative dominance of the concentric ribs. 



Textivemis, Cossmann. — Two small Eocene shells were separated 

 under this name by M. Cossmann in 1886, on account of their 

 remarkable surface-sculpture. This consists of fine divaricate raised 

 thread-like ridges, which cross one another in trellis-fashion on the 

 ventral portion of the valves. I place these shells under Chione, 

 because they agree with species of that genus in all essential 

 characters, excepting only in the crenulation of the inner margins, 

 which are smooth ; but the outer layer of the shell with its raised 

 pattern projects slightly beyond the inner layer, and forms a narrow 

 frilled or festooned border. 



The type of this subgenus is Venus texta, Lam., and it differs from 

 Mercimonia in having an impressed lunule, and an escutcheon bordered 

 by a ridge where the sculpture ceases. The teeth are more widelj^ 

 divergent, and the left median has a tendency to become bifid. The 

 pallial sinus is fairly deep and angular or subangular. 



17. Baeoda, Stoliczka, and Venekella, Cossm. PI. VI, Fig. 12. 



The type of this genus was described by d'Orbigny under the 

 name of Venus fragilis,^ and was separated by Stoliczka in 1871 

 under the name of Baroda, two other species from the Cretaceous 

 rocks of India being at the same time described. The group is placed 

 both by Fischer and Dall as a subgenus of Tapes, but the characters of 

 the hinge seem to remove it so far from Tapes proper that it is more 

 convenient to regard it as a distinct genus, especially as I find 

 a close relationship between it and Venerella, in spite of the difference 

 in shape. 



In Baroda the arrangement of the hinge-teeth is as follows : — In 

 the right valve two short entire teeth under the umbo, sometimes 

 slightly divergent, sometimes both directed forward; a posterior 

 tooth also entire, elongated, and directed backwards, while the space 

 intervening between it and the other teeth is deeply indented or 

 excavated. In the left valve the teeth are similar, but more equally 

 divergent, and the hinge-plate is excavated between each of them. 



The only recent species of Tapes which shows an approach to the 

 Baroda type of hinge is 2\ sidcaria, Lam., the hinge-plate of which 

 is similarly excavated, but in the right valve both the median and 

 posterior teeth are bifid, and the latter is much shorter than in 

 Baroda, while in the left valve the median is a broad triangular bifid 



' PaUcoBt. Frau9. Terr. Cret., vol. iii (1844), pi. 385, figs. 11, 12. 



