100 EOCENE MOLLUSC A. 



oblique j radiated or obsoletely costulated, finely decussated ; margin toothed, area of 

 connector rather narrow ; beaks depressed. 



Diameter, 2 inches. 



Localities. Stubbington {Edwards). 



Belgium: Le calcaire d'Afflighem et d'Audenarde, Kleyn Spauwen (Nyst). 

 France: Grignon, Courtagnon (Desltayes). 



A large number of fossils from various localities and from various formations have 

 been figured and described under the above name ; Brongniart has given it to a species 

 from the neighbourhood of Turin, and Dubois to one from Volhynia, but these are, perhaps, 

 not strictly within what are called specific limitations. The principal character, as its 

 name imports, is a tumid or puffed-up appearance of the specimen, with a very slight 

 deviation from the orbicular or rather circular form of the margins. There is also a 

 slight angularity on the siphonal region, as is often the case in shells of this genus. The 

 dental area is curved and well furnished with teeth, and the area for connexus is rather 

 small, but it increases considerably as the shell enlarges, and it is comparatively wider in 

 the old shell, where the ligamental portion of the connector has obliterated or overlapped 

 the denticles in the centre of the hinge area. The surface of the English specimens is 

 seldom or never in such a good state of preservation as those from the Paris basin, where 

 the small interstices between the rays and the lines of growth may be distinctly seen, 

 giving a slightly punctured appearance to the exterior, and in those shells a portion of the 

 connector is often preserved. 



8. Pectunculus quasipulvinatus, S. Wood. Tab. XVI, fig. 1, a, b. 



Spec. Char. P. testa lenticulato-complanatd, compressd, aquilaterali, cequivalvi, sub- 

 transversd; radiato-striatd, striis depressis, obsoletis ; concentrice decussatd ; marginibus 

 crenulatis ; area connexus perangustd ; umbonibus depressiusculis. 



Shell compressed or depressedly lenticular; equilateral, equivalve, rather transverse or 

 elongated ; covered with depressed and obsolete striae ; decussated by obscure or irregular 

 lines of growth ; margins crenulated ; area of connector narrow ; beaks depressed. 



Diameter, 2|th inches. 



Locality. Bracklesham. 



This has hitherto been placed in cabinets under the name of P. pulvinatus, var., but I 

 think the differences are such as to entitle it to a separate specific position, and the speci- 

 mens themselves appear to show a permanence of difference which give them as good a 

 claim for isolation as most others in this perplexing genus. Our shell is much more com- 

 pressed than the true pulvinatus, and the proportions in this are also different, the shell 

 being more transverse or elongated. It differs also from the French shell called pseudo- 

 pulvinatus, which is neither so compressed nor so transverse as our present species. I 



