BIVALVIA. 33 



PECTEN RUSHDENENSIS, Lye. Tab. XXXTIT, figs. 4, 4 a, 4 b, 4 c. 



Testa aquivalvi, suborbiculari, acuta, auriculis incequalibus (auricula antica majord), 

 valvis plano-convexis rugis concentricis elevatis, crebris, inferne squamatis, squamis brevilms, 

 reffularibus delicatissime instructis. 



Shell equivalve, suborbicular, acute, moderately convex ; auricles unequal (the anterior 

 one being the larger) ; the valves have a few plications of growth, and very densely arranged, 

 elevated, concentric rugas, which are slightly wrinkled towards the apices, but towards the 

 middle of the valves become short, regular, scabrous elevations, disposed checker-wise with 

 those above and beneath, so that when viewed obliquely the ornamentation resembles 

 that of an engine-turned watch ; this is more especially the case with the surface of the 

 right valve, which has the concentric rugae more delicate and closely arranged, and also 

 the scabrous elevations ; in other respects the valves are alike in the design of their 

 ornamentation. 



A beautiful suborbicular species ; the minute scabrous elevations arrest the finger when 

 it is passed upwards over the surface. It is very rare. 



Geological Position and Locality. The Cornbrash of Rushden, Northamptonshire, in 

 the collection of the Rev. A. W. Grieshach. 



PECTEN WOLLASTONENSIS, Lye. Tab. XXXIII, figs. 2, 2 a, 2 b, 2 c. 



Testa ovato-orbiculari compressa, ceqvivahi, aurieulis inaqualibus transverse plicatis et 

 radiatim costatis ; valva dextra concentrice striata et radiatim costata ; striis tenuissimix, 

 inferne lamelloso-rugosis ; costis in&qualibus nodosis ; numerosiu, inferne evanescentibus ; 

 valva sinistra striis subtittissimis concentricis reffularibus. 



Shell ovately orbicular, slightly convex, equivalve, with unequal auricles, the anterior 

 one being the larger ; they have numerous transverse plications and two or three radiating 

 costae ; the surface of the right valve has concentric striations and radiating costa? ; the 

 striations are very fine and irregular ; the middle and lower portion of the valve is occupied 

 by irregular, scabrous, concentric plications ; the radiating costse are very numerous, 

 irregular, and knotted ; they gradually disappear towards the middle of the valve. The 

 left valve has very delicate, regular, concentric, densely arranged striations. 



This rare Pecten differs from Pecten Di/onisius, Buv., chiefly in being equivalve, and in 

 the dissimilarity of the ornamentation in the opposite valves. 



Geological Position and Locality. The Great Oolite of Wollaston, Northamptonshire, 

 in the cabinet of the Rev. A. W. Griesbach. 



