36 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
costee, whereas /7. abjectus cannot be said to have any intercostal spaces, every part of the 
surface being occupied by unequal, crowded, nodose costz ; the two large, radiating, nodose, 
elevated varices are alike in both species. 
‘The specimen figured is the original example, which belonged to Mr. Bean ; it has lost 
a portion of the surface near to the lower border, and also a portion of the apex, nor will 
it appear remarkable that only a single specimen of a shell so thin and fragile should have 
been disengaged from a rock so intractable as the Cornbrash of Yorkshire. 
Geological Position and Locality. The Cornbrash of Scarborough, in the collection of 
Mr. Leckenby. 
Avicuna cuaTHrata, Lyc. Tab. XL, figs. 7, 7 a, 76. 
Testa parva suborbiculart, convexo-plana, valva sinistra auriculis subequalibus magnis ; 
superficie costis radiantibus (circa 24) acutis, regularibus et nodosis, lineis concentricis dis- 
tantibus decussatis ; valva altera subplana, levigata, inornata. 
Shell small, suborbicular; the left valve with a low convexity, with large and nearly 
equal auricles; the surface of the valve has about twenty-four regular, acute, and slightly 
knotted radiating costee, which are decussated by a few distantly arranged, concentric, 
elevated lines; the costae radiate equally over the auricles and the middle of the shell. 
The right valve is more flattened, it is smooth and destitute of ornamentation. Diameter, 
* about three lines. 
Geological Position and Locality. The Great Oolite of Minchinhampton; a single 
specimen. 
AvicuLa suBcostata, Roemer, sp. ‘Tab. XL, fig. 24. 
Monoris suncostata, Roemer, Nord. Ool., p- 75, t. 4, p. 7. 
Testa orbiculart subobliqua, convexa, longitudinaliter costulata, subtillissime concentrice 
striata, costulis (10O—14) remotis superne evanescentibus, enequalibus, auricula levi, 
umbonibus minimis antrorsum incurvis. Valva sinistra. (Roemer.) 
Shell orbicular, rather oblique, convex, longitudinally costulated, and with very 
delicate concentric striations ; costellae (10—14) acute, distinct, rather unequal, and dis- 
appearing towards the umbo; auricles plain; umbo small, curved forwards. The right 
valve is not known. 
A small shell; much less convex, less oblique, with a shorter hinge-line and more 
delicate ribs than 4. costata, Sow. 
Geoloyical Position and Locality. The Great Oolite of Minchinhampton Common, at 
which place it is very rare. 
