BIVALVIA. 99 



6 Pectunculus proximus, S. Wood. Tab. XVI, fig. 5, a — c. 



Spec. Char. P. testa oblique suborbiculare, incequilaterali, crussd, ttimidd ; obsolete 

 eostulatd vel radiatd ; siphoni-regione subangulato ; umbonibus prominulis ; area connexus 

 obtuse triangulari ; dentibus numerosis. 



Diameter* 1| inch. 



Locality. Barton {Edwards). 



This species differs from P. puhinatus, with which it has been hitherto associated, in 

 being more oblique, more elevated, and less tumid, and there is always a greater extension 

 of the siphoni-lateral margin, with a depression or flattened space above a slight ridge, 

 extending from the umbo on that side, particularly in elevated specimens. The shell in 

 general has a greater diameter in the direction of its height, and in these specimens the 

 ligamental area is larger or higher, with the dental margin broader than in others ; but its 

 principal distinction is the angular ridge on the siphonal side. Tab. XVII, fig. 11, is 

 from Huntingbridge, and may, I now think, be referred to this species; it was at first 

 supposed to be a Limopsis, but the character which induced that name is probably acci- 

 dental ; it is, however, smoother and thinner than the generality of the Barton specimens. 



There are two or three species from the Paris basin to which our fossil bears a close 

 relationship, but to no one of them can I satisfactorily assign it. P. depressus (Desh.) 

 resembles it in outline, but our shell is neither depressed (" depressissima"), nor thin; it 

 is crenulated all round, not " mince et lisse anterieureraent et posterieurement ;" neither 

 is the " area ligamenti minima." 



7. Pectunculus pulvinatus, Lamarck. Tab. XVI, fig. 2, a, b. 



Pectunculus pulvinatus. Lam. Ann. du Mus., t. vi, p. 216, and t. ix, pi. 18, fig. 



9, a, b. 



— — Desh. Par. Foss., p. 219, pi. 35, figs. 15—17. 



— — lb. Coq. Caract. des Terr., pi. 5, figs. 9, 10. 



— — Bronn. Leth. Geogn., t. ii, p. 936, pi. 39, fig. 4. 



— — Gold/. Petr. Germ., p. 160, No. 5, pi. 126, fig. 5. 



— — Nyst. Belg. Foss., p. 250, pi. 19, fig. 8, a, b. 



— — J. Sow. in Dixon's Geol. of Suss., p. 93, t. 11, fig. 25. 



— — Bronn. Syst. der Urw., p. 52, pi. 5, fig. 13, 1824. 



Spec. Char. P. testa orbiculatd, venfricosd aut pulvinatd, subeequilaterali vix obliquatd, 

 striato-costidatd vel radiatd, teniie decussatd; margine crenato, crenulis brevibus ; area car- 

 dinali perangustd, umbonibus depressis. 



Shell orbicular or lenticular, ventricose or puffed up, nearly equilateral, slightly 



14 



