ADDENDA. 111 
cardinali obliquo, area cardinis longitudinaliter striatis, sulcis transversis magnis (A), 
dentibus obliquis internis paucis inconspicuis ; superficie plicis inerementi delicate instructis. 
Valva altera mediocri convexa. 
Shell fragile, ovately oblong; left valve anteriorly very convex, moderately thick, 
and steep; posterior side expanded, attenuated, and produced into a short wing; umbo 
prominent, acute, subterminal, the anterior wing being short; the hinge margin is 
oblique, of moderate length; the hinge area has two or three prominent longitudinal 
striations ; the cardinal transverse sulci, four in number, are large and irregular ; the 
internal oblique teeth are few and inconspicuous ; the surface with numerous delicate plica- 
tions of growth. ‘The other valve is of nearly equal convexity and more strongly plicated. 
A well marked convex species, with the hinge border moderately oblique, and the 
whole of the posterior side expanded and delicate. 
Geological Position and Locality. he Forest Marble of Farleigh and Pound Pill; in 
the collection of W. Walton, Esq. 
Gervitiia ornAtaA, Lyc. Tab. XXXVI, fig. 7. 
Testa parva, ovato obliqua ; valva sinistra conveaa, umbont prominente, dla antica 
producta ; postica obliqua, brevissima ; superficie striis tenuissimis concentricis, regularibus, 
lineisque radiantibus decussatis. Valva altera ignota. 
Shell small, ovately oblique; the left valve inflated, the umbo prominent and situated 
nearly in the middle of the hinge line, which slopes from it obliquely in upon each side ; 
the anterior wing is produced and rounded, the posterior wing is very short; the surface 
of the valve has very delicate, regular, concentric striations, which are decussated by 
elevated lines which diverge from the umbo. ‘The other valve is unknown. 
A short, oblique, and very convex Gervillia; the radiating lines upon the middle of 
the valve are slightly undulating and conspicuous, but gradually disappear towards the 
sides. ‘The general figure is allied to G. ovata, Sow., but the latter is less convex, and its 
surface is destitute of ornamentation. 
Length, 5 lines; breadth, 3 lines. From the position of the shell in our figure the 
short posterior wing is not seen, and the convexity is scarcely sufficiently conspicuous. 
Geological Position and Locality, The Great Oolite of Bussage, adjoining Bisley 
Common ; collected by E. Witchell, Esq. 
Gervinuia Bicostata, Lyc. ‘Tab. XL, fig. 21 
Testa per-obliqua, convexa, ala antica brevi, altera longiora, emarginata, dorso, costis 
obliquis elevatis (2) distantibus, plicis incrementi maynis decussatis. Valva dewxtra 
agnota. 
