60 CRETACEOUS LAMELLIBRANCHIA. 



Measurements : 















(i) 



(2) 



(3) 



(4) 



(5) 



Length 



10 



10 



9-5 . 



9 



8 mm, 



Height 1 



17 



12 



10 



11 



. 9 „ 



(1) Hythe Beds (Bargate Stone), St. Katherine's Chapel, Guildford. 

 (2 — 5) Folkestone Beds, Folkestone. 



Affinities. — The shell in this species is smaller than in P. Cornueliana (see 

 above) ; also the main ribs on the left valve are closer together, more numerous, 

 and between them not more than one small rib is found. The ornamentation on 

 the right valve is very much finer than in P. Cornueliana. See also Pteria 

 (Oxytoma) tenuicostata (below). 



Type. — The type came from the Folkestone Beds of Risborough, but appears to 

 have been lost. Another specimen, however, from the same locality is in the 

 Fitton Collection in the Museum of the Geological Society. 



Distribution. — Hythe Beds (Bargate Stone) of St. Katherine's Chapel, Guild- 

 ford. Sandgate Beds of Parham. Folkestone Beds of Folkestone. Recorded by 

 Topley from the Hythe Beds of Hythe. Gault of Folkestone (British Museum, 

 No. L, 4920) . 2 Upper Greensand of Ventnor, and Crook Hill, Cheddington 

 (Dorset). 



Pteria (Oxytoma) sp. Plate VIII, fig. J 5 a, b. 



Some very small examples of a Pteria similar to P. pectinata are found in the 

 Totternhoe Stone of Hitchin. They are not well preserved, but appear to be dis- 

 tinguished from P. pectinata by the presence of transverse ribs placed at regular 

 distances in the spaces between the radial ribs. 



Pteria (Oxytoma) dubia (Etheridge), 1881. Plate VIII, fig. 16 a, b. 



1881. Avicttla dubia, B. Etheridge. In Penning and Jukes-Browne, Geol. Cam- 

 bridge, p. 145, pi. ii, figs. 4, 4 a. 



Remarhs. — This is known oidy by the two type specimens — one being a right 

 valve separated from the matrix, the other a left showing the interior only. The 

 surface of the right valve is smooth. Since the exterior of the left valve is un- 



1 Measured obliquely to the hinge-line. 



2 The species recorded from the G-ault of Folkestone as Avicula Bauliniana, d'Orbigny (see Jukes - 

 Browne, ' Cretaceous Rocks of Britain,' vol. i, p. 465), is probably Pteria pectinata. 



