BIVALVIA. 85 



Localities. The vertical range of this remarkable species is very considerable ;. it occurs 

 in the Inferior Oolite of the Cotteswolds, the Great Oolite of Minchinhampton, the 

 Coralline Oolite of Malton, and we have seen fine casts from the Kimmeridge Clay of 

 Wilts. The Hippopodium Luciense and H. Bajociense, D'Orb., are probably identical with 

 this species. 



Astarte excavata, Sow., var. compressiuscula. Tab. TX, fig. 18, 19. 



Astaete excavata, Sow. Min. Con., t. 233. 



— complanata, Roemer. Nordd. Oolith., t. 6, f. 28. 



Testa ovald, transversa, compressd, umbonibus parvis anticis depressis, margine cardinali, 

 elongato, carvato, subhorizontali, margine inferiore elliptico, lunula angustd excavata, 

 margine acuto. Costis externis concentricis depressis irregularibus interdum confertis aut 

 enim obsoletis. JElate juniori testa planatd etfragili, costis paucis latis prominulis. 



Shell ovately transverse, compressed ; umbones small, anterior, and much depressed ; 

 hinge border elongated, nearly horizontal, and curved ; lower border regular, elliptical ; 

 lunule deeply excavated, its margins acute ; concentric costao depressed, irregular, some- 

 times nearly obsolete. In the young state the shell is flattened, very delicate, pellucid, and 

 has a few distinct broad concentric costae near to the umbones. 



In the shelly beds of the Great Oolite, the young delicate shells occur abundantly from 

 3 to 6 lines in length. Adult specimens are much more rare, and few exceed 20 lines in 

 length. 



The tenuity of the test is considerable ; and this feature, together with the greater- 

 flatness, will serve to distinguish it from the typical form, A. excavata, Sow., which is a 

 much larger and thicker shell. Notwithstanding its tenuity, flatness, and the small 

 dimensions, we believe this to be only a variety of the well-known Inferior Oolite shell, 

 induced by peculiarities of the stratum in which it occurs. The same change of aspect takes 

 place in the freestone beds of the Inferior Oolite ; but the form again attains its pristine 

 dimensions and thickness in the upper ragstones higher in the series. 



Localities. Minchinhampton Common in the Great Oolite; Nailsworth Hill, in the 

 freestone beds of the Inferior Oolite. 



The typical shell occurs abundantly at Dundry and at Rodborough Hill. 



Astarte depress a, Gold/. Tab. IX, fig. 11. 



Astarte depressa, Goldfuss. Petref., p. 192, t. 134, f. 14. 



Testa compressd, transversim ovato-orbiculari ; umbonibus medianis obtusis ; lunula 

 ellipticd, angustd, costis convexis interstiisque concentrice striatis. (Goldfuss.) 



Shell compressed, transverse, ovately orbicular ; umbones median, prominent, obtuse ; 



