106 EOCENE MOLLUSCA. 
This species appears to be restricted to the uppermost deposits; I have not seen it 
from below the Barton beds. It is not rare, though by no means so abundant as the 
Paris Basin shell. On comparing the British fossil with the French species, the following 
differences may be observed. Our shell is shorter, more elevated, and more regularly 
ribbed in the direction of the lines of growth; the angle on the siphonal region is sharper 
and more distinct, and there are only small, fine, and very faint rays upon the edge of the 
pedal region, whereas in the French shell these rays are few, large, sharp, and very pro- 
minent. ‘The exterior of our shell has faint radiating lines, only perceptible in very perfect 
specimens, and by the assistance of a magnifier; they are most distinct on the siphonal 
region, particularly beyond the angular slope near the siphoni-lateral margin. The number 
of denticles are fewer in our shell than in the French specimens. It may be called var. 
delte-formis. 
2. Triconoc@1ia canceLLata, Deshayes. Tab. XIX, fig. 12. 
TRIGONOC@LIA CANCELLATA. Desh. An. sans Vert. du Bass. de Par., t. i, p. 838, pl. 64, 
figs. 31—35, 1860. 
Spec. Char. T. “ testa transversim trigond, inflata, subequilaterali, antice obtusd, postice 
acute angulatd, striis longitudinalibus, transversalibusque, eleganter decussatd, ad latus anti- 
cum longitudinalibus, proeminentioribus, distantioribus ; latere postico plano, ovato, angulo, 
acuto, aliquantisper proeminenti separato, liris tenuibus distantibus ornato ; cardine brevi, 
angusto, paucidentato ; dentibus minimis, sepius complicatis, fossuld ligamenti satis lata, 
regulariter triangulart.” —Desh. 
Shell elongately trigonular, slightly inflated ; subequilateral; pedal region the larger, 
somewhat inflated; pedilateral margin rounded; siphonal region slightly compressed, 
angular, with pointed termination; exterior radiated and decussated by prominent and 
regular lines of growth ; hinge-area small, denticles few ; depression for connexus broadly 
triangular and shallow. 
Length, } an inch. 
Localities. Wuntingbridge. 
France: Parnes, Damery-Auvers, Acy, Mary, Caumont, Crouy, La Ferte- 
sous-Jouare, Le Fayel (Deshayes). 
A single specimen only of this species has been obtained by Mr. Edwards, and that 
unfortunately is not quite perfect ; a part of the hinge-area has been destroyed, but the 
exterior and general contour of the shell correspond with the French species, and it may 
fairly remain with the above name for the present. It is quite distinct from our de/foidea. 
