74 SUPPLEMENT TO GREAT OOLITE MOLLUSCA. 



thickness towards the borders, the outline has a considerable resemblance to Lucina 

 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 Leckenbyi, Wright. Tab. XLII, fig. 3. 



Testa crassa, transversa, ovata, suhdepressa, umhonihus parvis, prominulis antero- 

 medianis ; latere antico brevi, margine rotundo, lunula subnulla ; latere postico j)roducto, 

 tnargine superiori subrecto, elongato, oblique declivi ; basi arcuato curvato ; superjicie 

 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 obhquely ; the base is elliptically curved ; the 

 surface has prominent, concentric, closely arranged, rounded rugas 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 rngse 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 A. detrifa, Goldf. ; the depressed figure, lengthened, straight, upper margin, 

 and large rugse, 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, in hard, gray 

 limestone. 



Astarte robusta, Lye. Tab. XXXV, figs. 6, 6 a. 



Testa parva suborbiculari, perinjlata, umbonibus magnis medianis incurvis, margine 

 posteriore et inferiore rotundo, lunula magna concava marginibus rotundis ; valvis costis 



