ADDENDA. 113 



conccntricis instructis. Area cardinis angusta, elonyata, foveolis (8) latis, subcon- 

 cavis. 



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

 valve ; test thick, umbones 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, Sckloth. Tab. XL, fig. 14. 



PECTEN SUBSPINOSOS, Schloth. Petref., p 223. 



Goldfuss. Petref., t. 90, fig. 4. 



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

 5, 6. 



Testa ovato-orbiculari fornicata aquivalvi, co-stis (12) aqualibus elatis subacutis in dor so 

 spinosis, sulcis conformibus transversim lineatis, auriculis inaqualibua costatis lincisque 

 dccussantibus striatis. (Goldfuss.) 



Shell ovately orbicular, equivalve; costae (12) large, elevated, subacutc, 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 Earleigh, 

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

 Quenstedt are Bopfingen and Waldenburg, in the Parkinson! Oolite and the Bradford 

 Clay ; also Nattheim, in the Coralline Oolite. 



MACRODON HIRSONENSIS, var. RUGOSA. Tab. XXXVI, fig. 9. 



The Forest 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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