38 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
Perna Fotiacka, Lyc. Tab. XX XVII, figs. 3, 3a. 
Testa ampla subequivalvi, subplana, umbonibus prominulis acutis; latere antico 
excavato, margine posteriore et inferiori elliptico curvato; lateribus rugis concentricis 
paucis irregularibus. Foveolis interni ignotis. 
A large, subzequivalve, depressed shell, with prominent, pointed umbones, excavated 
and thickened anterior border, the hinge-line short, the posterior and inferior borders 
elliptically rounded, the general figure being mytelliform, the left valve being somewhat 
more convex than the other; the test is thin, with delicate margins. 
Dimensions. Length, 43 inches; opposite diameter, 23 inches; the hinge-area has 
not been exposed. 
Geological Position and Locality. The Great Oolite of Minchinhampton Common ; 
a single fine specimen of each valve is in the collection of the author, who is not cognizant 
of any other examples. 
INoceRAMUS QuaDRaTUus, Sow., sp. Tab. XXXVIII, figs. 1, la, 14. 
PERNA QUADRATA, Sow. Min. Con., t. 492, non Phil. non Goldf. 
— - Lycett. Aun. and Mag. Nat. Hist., 1855. 
Testa tenue subquadrata, transversa, inequivalvi, valde inequilatera, valva sinistra 
antice oblique inflato, postice compresso ; umboni magno, subinvoluto, antrorsum instructo ; 
linea cardinali subhorizontali elongato ; latere anteriore truncato, infra umbonem concavo, 
basi subrecto, superficie rugis concentricits paucis irregularibus. Valva dextra planata 
wmboni parvo antico.  Foveolis interni parvis numerosis. 
Shell thin, subquadrate, transverse, inequivalve. The left valve inflated anteriorly, 
with a large, subinvolute, projecting beak, and a steep, truncated and excavated slope 
beneath it; the posterior side is very thin, compressed, and expanded ; the hinge-line is 
lengthened and nearly horizontal; the base is lengthened and nearly straight. The right 
valve is flattened; the umbo is small, pointed, and anterior, The internal hinge-pits are 
placed upon a narrow, lengthened plate ; they are small and numerous. ‘The surfaces of 
the valves are smooth, with a few irregular, concentric plications. 
The diagnosis in the ‘ Mineral Conchology’ is as follows :—“ Quadrilateral, one side 
shorter than the other three; valves gibbose, unequal, the shorter side very concave, 
bounded by two obtuse carine.” 
The figure in the ‘Mineral Conchology’ has the right or smaller valve facing the 
spectator ; the contour of the larger or convex valve is not seen ; even the outline is not 
perfect, as there seems to be a portion of the lower (right) border wanting, and thus 
forming an angle at its anterior extremity, which would be rounded in the perfect shell ; 
but the whole is stated by the author to be little better than a cast. With such an 
