BAIRDIA SUBDELTOIDEA. 5 



been reproduced here. The new fig. 65, of a specimen from the Chalk -marl at 

 Didcot railway-station, Berkshire, gives a good idea of the exterior of a right valve 

 of this species. It is longer than P. triquetra, less triangular, with a well-rounded 

 anterior margin, and proportionally less arching of the back. The greatest 

 thickness is at the posterior third. The surface is minutely punctate. 



Edge view, lanceolate ; end view, acute-oval. 



This form, at first sight, seems to be near to the recent P. trigonella^ Sars ; 

 but it is rounder in front, and the greatest thickness is behind the middle of the 

 valves. We propose to associate with this elegant form the name of the late 

 eminent Ostracodist, J. Bosquet, of Maastricht. 



In a carapace valve in Mr. F. Chapman's collection from the Gault of Folke- 

 stone Mr. Sherborn has recognised the occurrence of distinct muscle-spots — 

 consisting of a curved row of four (convex downwards) with two above — very 

 similar to figs. 1 e and 8 e in pi. i of the ' Monogr. Tert. Entom.,' 1857, but in a 

 reversed position. 



Localities. — Figs. 18/, /', in Pi. VI, 1849, represent the interior of a left valve 

 from the Oault of Folkestone. PL IV, fig. 3, reproduces 18/. PI. II, fig. 65, 

 illustrates a specimen from the Chalk-marl at Didcot station, Berks ; and with a 

 high power the surface is seen to be beset with distinct pimples, but very small 

 and irregularly scattered. On another specimen, from Folkestone, minute puncta- 

 tions appear to be characteristic. 



III. Bairdia, M'Coy, 1844. 



1. Bairdia sdbdeltoidea {Milnster). Plate II, figs. 31 — 34 (refigured^ from 



the figs. 15 a — d of the Monograph, 

 1849 ; but figs, e, /, /', /", /", have 

 not been reproduced). 



Cttheee SUBDELTOIDEA, Munster. Jalirb. f. Min., &c., 1830, p. 64, No. 13 ; 



1835, p. 446. 

 CxTHEEiNA SUBDELTOIDEA, Eomer. Neues Jatirb. f . Min., &c., 1838, p. 517, pi. vi, 



fig. 16. 



— — — Verstein. uordd. Kreidegeb., p. 105, pi. xvi, 



fig. 22. 



— — Beuss. Verstein. bohm. Kreideform., pt. 1, 1845, 



p. 16, pi. V, fig. 38 ; pt. 2, p. 104. 



1 'Monograpb Post-Tertiary Entom.,' Pal. Soc, 1874. 



2 The postero-ventral edge in fig. 34 has been serrated by mistake ; it should be regular and 

 entire, like that in fig. 33. The prickles introduced, from optical illusion, in fig. 15 J are neces- 

 sarily omitted in fig. 34. 



