30 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



BIVALVIA. 



Gryph^a minuta, Sow. Tab. XL, fig. 30. 



Gryph^a minuta, Sowerhy. Min. Con., tab. 547, fig. 4. 

 — — Morris. Catal. Brit. Foss., p. 186. 



Testa parva, valva majora suhorhiculata, umboni incurvo, latere untied sulcd brevi 

 instruetd. Valva altera ignota. 



Shell small ; the larger valve subglobose, suborbicular ; the beak produced, incurved, 

 and nearly straight, only slightly roughened by the area of attachment ; the anterior side 

 with a short sulcation, but no distinct lateral lobe. The smaller valve is unknovv^n. 



A minute Gryphaea, of which several specimens have been obtained by Mr. Witchell 

 in the Minchinhampton Great Oolite ; it has no well-defined distinctive features, and 

 would scarcely have been deemed worthy of notice had it not been figured by Mr. Sowerby 

 from Ancliff. 



Placunopsis semistriatus, Bean, sp. Tab. XXXIII, figs. 9, 9 a. 



Anomia semistriata. Bean. Mag. Nat. Hist., 1839, p. 61, fig. 21. 



Testa, valva viajora convexa, mbobliqua, ovato rotundata, apice submarginali, acuta, 

 lamellis concentricis, irregularibus, superne laevigata, in/erne lineis radiantibus subcequalibus 

 nodulosis ornata. Valva ajjixa ignota. 



Shell with the larger valve ovate, slightly oblique, convex; the apex pointed, and 

 placed near to the margin ; the surface has numerous irregular, concentric lamellae ; the 

 lower portion has numerous radiating lines, which are nearly equal, granulated, and 

 undulated. The attached valve has not been obtained. 



The test appears to be less delicate than is found in some other examples of the genus, 

 and is usually affixed to another shell, more especially to Terebratula lagenalis, so that it 

 is scarcely possible to obtain a specimen whose figure has not been afiected by some 

 extraneous body. The general aspect has much resemblance to Placunopsis Jurensis 

 {' Gr. Ool. Monog. Biv.,' tab. i, fig. 13), but the latter has the ornamentation of the 

 surface much more strongly defined, with larger and more densely arranged radiating lines. 

 In P. semistriatus these can only be discerned with a magnifier. 



Geological Position and Locality. The Cornbrash of the Yorkshire Coast, at Gris- 

 thorpe and Scarborough, where it is moderately rare. The upper portion of the 

 Inferior Oolite in the Cotteswold Hills has a species probably identical with this Pla- 

 cunopsis, and possessing a similar kind of ornamentation. 



