138 JOURNAL OF CONCHOLOGY, VOL. 15, NO. 5, JANUARY, I917. 



Beyrich's Fusus sexcostaius, a characteristic fossil of the Upper Mio- 

 cene formation of North Germany. He was further of opinion that 

 tlie Lenham beds were older than had hitherto been supposed, and 

 he considered that they should be referred to the Miocene period. 



Explanation of Plates. 



The figures are of natural size unless otherwise specified. The letters M.P.G. or B.M. 

 indicate that the specimens figured are either in the Museum of Practical Geology or 

 in the British Museum (Geological Department). The British Museum specimens were 

 chiefly collected and presented by Mr. Graham Wallas, while a few were obtained in 

 exchange from Mr. A. S. Kennard, F.G.S. 



PLATE I. 



Pelecypoda (extinct). 



Chlamys princeps J. de Sowerby, sp. 

 Fig. I. — Umbonal region of a left valve, showing external characters. 



From a gutta-percha model. 

 Fig. 2. — Magnified view of the costal rays of same specimen, with 



scabrous ornamentation. [M.P.G., No. 404]. 



HiNNiTES CRisPUS Brocchi, sp. 

 Fig. J. — Lateral view of fragmentary left valve, in which the costae 

 are more regular and equi-distant in the early stage than 

 during the subsequent period of growth ; obscure spinous 

 thickenings are traceable on the later costae. From a gutta- 

 percha model. [M.P.G., No. 401]. 



Tellina benedeni Nyst and Westendorp. 

 Fig. 4. — A natural internal sandstone cast of a right valve, exhibiting 

 the ovately trigonal contour of this species, the adductor 

 scar impressions, and the extensive pallia! sinus. 



[B.M., Graham Wallas Coll.]. 



Arcopagia ventricosa Serres, sp. 



Fig. J. — Lateral aspect of a right valve, showing the close and well- 

 marked concentric costse associated with fine and equi-distant 

 radial striations. From a gutta-percha model. 



Fig. 6. — Magnified portion of surface of same specimen, exhibiting a 

 latticed structure. [M.P.G., No. 425]. 



Plagiocardium hirsutum Bronn, sp. 



Fig. 7. — Externo-lateral view of a right valve, showing the narrow 

 sulcations between the costse. From a gutta-percha model. 



Fig. 8. — Magnified surface of same, indicating the squamose char- 

 acter of the costas. [M.P.G., No, 420]. 



