ADDENDA. Ill 



cardinali obliquo, area carilinis longitudinaliter striatic, sulcis fransversh mat/nis (4), 

 dentibus obliqiiis intcrnis paticis inconspicuis ; superjicie plicis incrementi delicate instriiciis. 

 Valva altera mediocri convexa. 



Shell fragile, ovately oblong; left valve anteriorly very convex, moderately thick, 

 and steep; posterior side expanded, attenuated, and produced into u short wing; umbo 

 prominent, acute, subterminal, the anterior wing being short ; the hinge margin is 

 obli(|ue, 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. 



Geolo(jical Position and Locality. The Forest Marble of Parleigli and Pound Pill ; in 

 the collection of W. Walton, Esq. 



Gervillia ornata, Lye. Tab. XXXVI, fig. 7. 



Testa parva, ovnto obliqua ; valva sinistra convexa, umboni jjrominente, ala anfica 

 producta ; postica obliqua, brevissima ; superjicie 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. Prom the position of the shell in our figure the 

 short posterior Aving 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. 



Gervillia bicostata, Lye. Tab. XL, fig. 21. 



Testa per-obliqua, convexa, ala antica brevi, altera longiora, emarginata, dorso, costis 

 obliquis elevatis (2) distantibus, plicis incrementi magnis decussati>i. Valva dextra 

 ignota. 



