98 EOCENE MOLLUSCA. 



4. Pectunculus globosds, J. Soicerbg. Tab. XVI, fig. 9. 



Pectunculus globosus. J. Sow. in Dixon's Geo], of Sussex, p. 170, t. 3, fig. 20, 1850. 



Spec. Char. P. testa crassd orbicularis globosd, sub-aquilaterali, aquivalvi, laevigata, 

 ant obsolete radiatd ; margine cardinali arcnatd, timbonibus prominentibus, marginibus 

 crenulalis. 



Shell thick, obliquely orbicular, globose, slightly inequilateral, equivalve, smooth, with 

 faint or obsolete radiations ; hinge or dental area curved ; beaks prominent ; margins 

 crenulated. 



Diameter, 1 inch. 



Localitg. Bracklesliam {Dixon). 



This appears to be more tumid at the upper part than any other species. There is 

 a resemblance between it and jproximits, which is common at Barton ; but that shell is 

 always more or less oblique, with a sharper or less tumid umbonal region, and this shell, 

 as its name implies, is more globose. 



5. Pectunculus Plumsteadiensis, /. Sowerby. Tab. XVI, fig. 6, a, b. 



Pectunculus Plumsteadiensis. J. Sow. Min. Con., t. 27, fig. 3, 1813. 

 — — Morris. Catal. Brit. Foss., p. 219, 1854. 



Spec. Char. P. testa tenui, lenticulari vel orbiculato-subquadratd, aquilaterali ; 

 obsolete costatd vel radiatd, concent rice striata ; umbonibns deprcssis ; marginibus crenulatis ; 

 area connexiis parvd. 



Shell thin, lenticular, with a somewhat roundedly quadrangular outline ; equilateral, 

 obsoletely costated or radiated ; beaks depressed, with a small area for the connector ; 

 margins toothed. 



Diameter, \\ inch. 



Localities. Plumstead ; Upnor ; Katesgrove, near Reading. 



This is thinner than the generality of the genus, and the rays upon the exterior are 

 broad and rounded ; it resembles brevirostris in having a small beak, but that shell is 

 more oblique, with the rays less prominent, the hinge less curved, and the denticles fewer. 

 In the ' Gcol. Journ./ vol. x, p. 120, 1854, this species and brevirostris are united with 

 P. terebratularis, Lamarck. M. Deshayes (p. 852) considers the two latter as distinct, 

 and I am disposed to agree with him, but I believe also that the above-named Plum- 

 steadiensis is entitled to a distinct specific position. 



