112 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



Shell small, very oblique, convex ; the anterior vi'ing short, thick, and gibbose ; 

 posterior wing more lengthened, emarginated posteriorly ; the middle of the valve with 

 two elevated, oblique, longitudinal, distantly arranged costse, which are crossed by large 

 irregular folds of growth ; the right valve has not been obtained. 



Our sole specimen has the posterior extremity imperfect. 



Geological Position and Locality. The Great Oolite of Bussage, near Bisley 

 Common ; collected by E. Witchell, Esq. 



Perna Mytiloides, Lam. Tab. XXXII, fig. 3. 



Perna Mytiloides, Lamark. An. sans Vert., 6 Bd., p. 142. 



— — Zieten. Pet., p. 71, pi. 54, fig. 2. 



— — Gold/. Pet., p. 104, t. 107, fig. 12. 



— — UOrb. Prodrome de Paleont., 1, p. 311, No. 211. 



— — Morris. Catal., 1854, p. 179. 



— — Oppel. Jura formation, p. 607, No. 79. 



— — Quenstedt. Der Jura, p. 383, tab. 52, fig. 8. 



— — Damon. Geo). Weymouth, Suppl., pi. 2, fig. 5. 



Testa ovata-sipnoidea, convexo-plana in alani brevem prodmta, umbonibus acutis 

 prominentibus, margine cardinali obliquo,foveoUs {8-\2) plano-concavis. 



Shell thick, ovately sigmoidal, with a moderate convexity, slightly produced pos- 

 teriorly into a short imperfect wing; the hinge margin is wide, oblique with transverse 

 pits from eight to twelve in number, and only slightly impressed ; the anterior border of 

 the valves is much thickened and excavated. 



Geological Positions and Localities. The Porest Marble of Farleigh ; in the cabinet 

 of W. Walton, Esq. Unfortunately none of the Porest Marble specimens are altogether 

 perfect. The Geological range of this Perna must be very considerable, if there is no 

 mistake in the identification of the species. Professor Quenstedt records it in the 

 Inferior Oolite of Wurtemburg; Goldfuss, in the Oxford Clay and Upper Oohte of 

 Baireuth and Wurtemburg; D'Orbigny quotes it from Villiers, Trouville, Lyon, 

 Chaumont, Pizieux, Marolles (Sarthe), and other localities in the same department, 

 all in his ' Etage Callovien.' 



Mr. Damon has figured it from the Oxford Clay of Weymouth ; and it has been 

 recorded in the Kimmeridge Clay of the latter place ; and the Portland Oolite of Swindon, 

 by Professor Morris. 



Pern A obliqua, Walton MSS. Tab. XXXIV, fig. 22 a. 



Testa subaquivalvi convexo-plana, crassa, umbonibus acutis, prominentibus, margine 

 anteriore recto, margine cardinali recto, oblique declivi, valvis lamellis xrregulanbus 



