74 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 
thickness towards the borders, the outline has a considerable resemblance to Lwucina 
crassa but the latter is much thicker towards the borders of the valves, and has a different 
kind of surface. The hinge has not been exposed. 
Geological Position and Locality. The Cornbrash of Scarborough ; in the collection 
of Mr. Leckenby. 
Astarte Lucxensyl, Wright. Tab. XLII, fig. 3. 
Testa crassa, transversa, ovata, subdepressa, umbonibus parvis, prominulis antero- 
medianis ; latere antico brevi, margine rotundo, lunula subnulla; latere postico producto, 
margine superiort subrecto, elongato, oblique declivi; basi arcuato curvato ; superficie 
rugis crebris concentricis et striis subtilibus ornatis. 
Shell thick, transverse, ovate, rather depressed ; umbones small, prominent, placed at 
the commencement of the anterior third of the shell ; anterior side short, its margin 
rounded with scarcely any lunule; posterior side produced and compressed, its superior 
margin nearly straight, lengthened, sloping obliquely ; the base is elliptically curved; the 
surface has prominent, concentric, closely arranged, rounded rugz near to the umbones, 
which afterwards degenerate into depressed, irregular plications; there are also fine, con- 
centric striations. 
A large species, remarkable for the depression of the valves and for the great 
length and straightness of the superior border, whose measurement is equal to the 
height or to two thirds of the entire length of the shell; the rugze are so closely 
arranged near to the apex that upwards of thirty may be counted upon one fourth the 
height of the shell. 
From Astarte elegans, Sow., it is distinguished by the more lengthened, depressed 
figure, and by the absence of a smooth, excavated lunule; it is much less orbicular and 
convex than 4. defrita, Goldf.; the depressed figure, lengthened, straight, upper margin, 
and large rugze, will serve to distinguish it from other large ovate species of the lower 
Oolites. Specimens in Mr. Leckenby’s collection exceed three inches in length, It is 
not rare, but, in common with other large shells of the Cornbrash, it has usually undergone 
compression. 
Geological Position and Locality. The Cornbrash of Scarborough, i hard, gray 
limestone. 
Astarte roBusta, Zyc. ‘Tab. XXXV, figs. 6, 6a. 
Testa parva suborbiculari, perinflata, umbonibus magnis medianis incurvis, margine 
posteriore et inferiore rotundo, lunula magna concava marginibus rotundis ; valvis costs 
