ADDENDA. 113 



concentricis instructis. Area cardhns anyusta, elongaia, foveolis (8) latis, subcon- 

 cavis. 



Shell siibequilateral, moderately convex, slightly arched longitudinally in the left 

 valve ; test thick, unibones acute and prominent ; anterior border straight ; hinge-border 

 moderately lengthened, straight, sloping obliquely downwards. Hinge-area narrow, 

 elongated, pits (8) wide, and only slightly concave; lamellae of growth large and 

 irregular. 



Length, about twice as great as the transverse measurement ; diameter through the 

 valves, one third of the length. 



Geological Position and Locality. The Forest Marble of Gastard ; in the cabinet of 

 W. Walton, Esq. 



Pecten subspinosus, Scldoth. Tab. XL, fig. 14. 



Pecten subspinosus, SMotfi. Petref., p 223. 



— — Golf/fuss. Petref., t. 90, fig. 4. 



— — Quenst. Der Jura, p. 500, pi. 67, figs. 3, 4 ; and pi. 92, figs. 



5, 6. 



Testa ovato-orhiculari fornicata cBquivalvi, costis (12) aqualibus elatis snbacutis in dorso 

 spinosis, sulcis conformihus transversim lineatis, auriculis inaqualibiis costatis lineisque 

 decussantibus striatis. (Goldfuss.) 



Shell ovately orbicular, equivalve; costse (12) large, elevated, subacute, each having 

 upon its ridge a few short spines ; the interstitial sulcations are narrow, with delicate, 

 transverse lines ; the auricles are unequal, the anterior auricle of the right valve being the 

 larger ; they have radiating and decussating lines. The valves have but little convexity ; 

 the radiating costse form one third of a circle. 



Height, 7 lines ; transverse diameter, 9 lines. 



Geological Positions and Localities. The Forest Marble of Locus and Farleigh, 

 Somerset ; in the collection of W. Walton, Esq. The foreign localities cited by Professor 

 Quenstedt are Bopfingen and Waldenburg, in the Parkinsoni Oolite and the Bradford 

 Clay ; also Nattheipj, in the Coralline Oolite. 



Macrodon Hirsonensis, var. rugosa. Tab. XXXVI, fig. 9. 



The Eorest Marble of Wilts and Somerset has this species in the form of a variety 

 which is distinguished from the shell of the Inferior and Great Oolite by the following 

 features: — It has greater convexity, a wider hinge-area; the posterior side is more de- 

 pressed, and is not uncommonly traversed by two or three radiating furrows, and is in 

 some instances separated from the other portion of the surface by a distinct keel. The 



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