44 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
Cucutn#a cLaTHRATA, Leck. Tab. XXXIX, figs. 4, 4a. 
CucULLHA CLATHRATA, Leckenby. Journ. Geol. Soc., 1858, vol. xv, pl. 3, fig. 4. 
Testa subrhomboidali inflata, umbonibus antemedianis magnis, valde separatis, area 
ampla, excavata, lanceolata, bast subrecto; valvis rugis longitudinalibus, irregularibus, 
lineisque radiantibus, crebris tenuibus, dorso angulo obtuso et obliquo. 
Shell subrhomboidal, inflated ; umbones large, placed anterior to the middle of the 
valves, separated by a large lanceolate area; there is an oblique obtuse angle upon the 
posterior side, separating a concave posterior space from the middle portion of the valves; 
the surface has large, longitudinal, irregular, rugose plications crossed by closely arranged, 
delicate, radiating lines; the lower border is nearly straight, and slightly sinuated. 
The shorter posterior side and larger umbones distinguish it from Arca lata, Dunker, 
to which in other respects it has a considerable resemblance. 
Dimensions.—Length, 26 lines; height, 14 lines; diameter through both the valves, 
16 lines ; space separating the points of the umbones, 3 lines. 
Geological Position and Locality. The Cornbrash of Scarborough, also in the 
Kelloway Rock of the same locality. In the collection of Mr. Leckenby. 
Nvucuna Menxer, Roem. Tab. XXXIX, fig. 2. 
Nocuta Menxet, Roemer. Nordd. Ool., t. 6, fig. 10, p. 98. 
Testa ovata, medio ventricosa concentrice striata, antice brevissima acuta oblique 
truncata, cordato-subexcavata, posterius producta rotundata, basi subarcuata, umbonibus 
erassis incurvis, aream lanceolatam haud efformantibus. (Roemer.) 
Shell ovate, anterior side very short, somewhat excavated, and pointed at its lower 
extremity; posterior border lengthened, curved, sloping obliquely downwards, its lower 
extremity rounded, base slightly curved elliptically, umbones large, incurved, area very 
slightly defined ; the middle portion of the valves is moderately convex, with a few distant 
plications of growth, and delicate concentric striations obscurely defined. 
Nucula variabilis, Sow., approximates to this species, but is without the anterior 
excavation, and has a more lengthened posterior side. Nucula nuclens, Desl., is shorter 
and more globose. 
Geological Positions and Localities. Roemer records Nucula Menkei in the Portland 
Limestone of Wendhausen. Mr. Whiteaves has collected it in the Great Oolite of Kirk- 
lington, and in the Cornbrash of Islip, Oxon. 
