38 EOCENE MOLLUSCA. 
1. Pecren sexicostatus, S. Wood. Tab. VIII, fig. 11, a, 6. 
Spec. Char. Testd crassd, equivalvi, orbiculari vel lenticulari, aquilaterali, costata ; 
costis 20-24 sub-rotundis, striatis et imbricatis; ‘tnterstitiis lineatis et imbricatis ; 
auriculis magnis, inequalibus. 
Shell thick and strong, equivalved, orbicular or lenticular, equilateral, costated ; ribs 
20 to 24 somewhat rounded, striated, and strongly imbricated; interspaces also with 
imbricated rays : auricles large and unequal, one costated, the other striated. 
Diameter, 1:ths of an inch. 
Locality.—Brockenhurst (dwards). 
Our shell is a handsome one and highly ornamented, and, judging from the number 
of specimens in Mr. Edwards’ cabinet, it does not appear to have been scarce. In addition 
to the above formula, it may be further noticed, that the centre of the elevated rib is not 
only strongly and regularly imbricated, but the imbrices are long, overlapping, and 
slightly projecting ; they are not reflexed, but lie over each other like ornamental tiling ; 
there is a smaller ray on each side of the centre one, which is also imbricated, and the two 
lines or rays on the interspaces are likewise covered with small imbrications. The auricle 
on the pedal side of the right valve is a very large one, and ornamented with about half a 
dozen costee, while the other is only striated with numerous rays ; and the ears of the left 
valve are both striated ; angle of divergence, 90°. The nearest approach to this species is P. 
Thorenti, D’Archiac, Tr. Geol. Soc. Fr., 2d sér., t. xi, pt. 1, p. 211, pl. 8, figs. 8, 8, a, 6, 
which much resembles it in the ornament, but the auricle of that shell is so much 
smaller that I must presume the two to be different. The figure there taken was from a 
solitary specimen, and the auricle, if natural, does not appear to me to be perfect. 
2. Prcren carinatus, J. Sowerby. Tab. IX, fig. 5, a, 6. 
Pecren carinatus. J. Sowerby. Min. Conch., t. 575, 1828. 
— — Prestwich. Journ. Geol. Soc., 1847, p. 405. 
— — Morris. Cat. Brit. Foss., p. 178, 1854. 
Spec. Char. P. testd orbiculari, lenticulari, equivalvi, equilaterali, costatd ; costis 
(circa 20) subequalibus, rotundatis, in medio carinatis; interstitiis levibus ; auriculis 
subequalibus. 
Shell orbicular, lenticular, equivalved, equilateral, costated; ribs about 20, nearly 
equal, rounded, with a sharp keel along the centre of each ; interspaces generally naked, 
or only marked with fine lines of growth; auricles nearly equal. 
Diameter, 1 inch. 
Locality.—Barton. 
