﻿422 ME. L. RICHARDSON ON THE RHJ2TIC AND [Aug. I905, 



YIII. Pal^eontological Notes. 



Ostrea Bristovi, Etberidge, MS. (PL XXXIII, fig. 4.) 



Right valve. — The dimensions of an average-sized specimen 

 are : length 45 millimetres, breadth 55 mm. The greatest length 

 seems to be attained (as a rule) at 23 mm. from the most extended 

 portion of the ventral margin. The valve is flat or slightly convex ; 

 the ventral margin regularly convex ; while the anterior and pos- 

 terior margins converge regularly in the direction of the beak, 

 which unfortunately is not preserved in the specimens collected. 

 The test is somewhat thin for an Ostrea, and composed of numerous 

 considerably-imbricating layers. 



Unfortunately, the preservation of the specimens of this lamelli- 

 branch does not admit of a very exact diagnosis. Mr. E. T. Newton, 

 F.R.S., informed me (in Hit.) that specimens of this oyster are 

 preserved in the Museum of Practical Geology, Jermyn Street, 

 London, and bear the MS. name of Ostrea Bristovi, Etheridge. 



Like most of its tribe, this form is difficult to describe ; but, on 

 account of its frequent occurrence in the Lavernock area, it seems 

 desirable to have some name wherewith to record it when obtained. 



The specimen figured is from the upper portion of the Sully Eeds 

 (Hhaetic) at Cadoxton (Glamorganshire). 



Carditjm cloacinum, Quenstedt. (PL XXXIII, fig. 5.) 



1858. ' Der Jura ' Tubingen, p. 30 & pi. i, fig. 37. 



1856. Oppel, A., & Suess, E., ' Ueber die uiuthmasslichen iEquivalente der Kossener 



Schichten in Schwaben ' Sitzungsber. k. Akad. Wissensch. Wien, vol. xxi, 



p. 540 & pi. ii, fig. 2. 

 1904. Vaughan, A., ' The Rhastic Beds of the South- Wales Direct Line ' Quart. 



Journ. Geol. Soc. vol. lx, pp. 207-208 & fig. 6. 



In the immature forms of this shell the costsB are rounded or 

 subacute, and increase in breadth towards the ventral margin ; 

 while the intercostal spaces exceed the breadth of the costse. In 

 the adult forms, however, the costse are usually broader and flat- 

 topped, while the intercostal spaces are reduced to mere linear 

 grooves. 



The first definite record of this shell was at Wainlode Cliff 1 ; 

 but since then it has been found at many localities, and was 

 especially abundant at Lilliput, near Chipping Sodbury, on the 

 South-Wales Direct Line. Dr. Yaughan has given an excellent 

 description of the species, elucidated by figures in the text (Quart. 

 Journ. Geol. Soc. vol. lx, pp. 207-208), and has drawn attention to 

 the Oardita-like aspect of the shell, which is especially noticeable 

 in the specimens figured in the present paper. Charles Moore, 

 indeed, referred this shell (which he obtained from the railway- 

 cutting at Willsbridge, near Eitton) to the genus Cardita, and 

 entered it as such in his section (Quart. Journ. Geol. Soc. vol. xxiii, 

 1867, p. 498). His specimen is now in the Bath Museum, and 

 came from the Upper Khajtic. 



1 Proc. Cottesvr. Nat. F.-C. vol. xiv (1903) table i, facing p. 174. 



