84 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
rostrata, attenuata, area lata, plicis duobus longitudinalibus ; latere antico subcompresso, 
elliptico curvato, plicisque regularibus et longitudinalibus. 
Shell transversely elongated, very inaequilateral; umbones placed anterior to the 
middle of the valves, small, depressed, and anterior ; posterior side rostrated or attenuated, 
and much elongated; area large and wide, with two longitudinal ridges, in addition to a 
distinct marginal ridge which separates the area from the other portion of the shell; 
anterior side rather compressed, its border is curved elliptically ; the anterior portion of 
the sides of the valves have regular, longitudinal ridges and furrows, which disappear 
posterior to the umbones; the oblique sulcation which proceeds downwards from the 
umbones in all examples of Cercomya is only faintly impressed. 
The specimen figured has the general form of the shell unusually well preserved, but 
the test has disappeared ; the very inequilateral figure, with the attenuation and elongation 
of the posterior side, will readily distinguish it from Anatina undulata, Sow., as also from 
most other examples of the genus. 
Height, one third the length; diameter through both the valves, one fourth the 
length. 
Geological Positions and Localities. It occurs rarely in the Cornbrash of Scarborough. 
Professor Phillips has recorded it in the Oxford Clay, and Mr. Leckenby in the 
Kelloway Rock and Calcareous Grit of Yorkshire. M. Quenstedt quotes it from the 
Cornbrash of Wurtemburg; M. Agassiz from the Oxfordian Strata of the Vadois Jura and 
the Jura of Soleure. 
PHoLapomya ovuLuM, 4g. Tab. XXXV, figs. 18, 18 a. 
PHOLADOMYA OVULUM, 4g. Et. Crit. Myes., p. 119, tab. 3, figs. 7—9; tab. 3 4, 
figs. 1—6. 
— ~ D’Orb. Prodr., 11 ét., No. 168, vol. 1. 
— _ Morris. Catal. Brit. Foss., 1854, p. 221. 
— _— Oppel. Juraformation, p. 481. 
Testa ovato-elongata, antice breviore, rotundata, cordata, posterius producta, attenuata, 
margine inferiore arcuato curvato, superiore subhorizontali, concavo, umbonibis crassis 
subanticis prominulis ; valvis concentrice plicatis, plicis longitudinalibus numerosis in@- 
qualibus mediocriter tenuibus ; costellis radiantibus obliquis aequalibus angustis, inferne 
evanescentibus, apertura postico et antico angusto. 
Shell ovately elongated; the anterior side short, rounded, cordiform ; the posterior side 
produced and attenuated ; the inferior margin is curved elliptically ; the superior margin is 
moderately lengthened and concave; the umbones are elevated and tumid ; the sides of 
the valves are convex, with closely arranged but not prominent longitudinal plications ; 
the radiating cost are very narrow or linear, disposed obliquely, about twelve in number; 
