1850.] R. N. MANTELL ON THE OOLITE OF WILTS. 317 



A discoidal and somewhat gibbose shell, with rather depressed and 

 broad volutions, inner side obliquely angular, margined with about 

 fifteen prominent rounded tubercles, from each of which arise two or 

 three obtuse costse passing over the broad convex back ; these costse 

 become obsolete in an adult state. 



Aperture transverse, semi-elliptical. Thickness 4^ inches, diameter 

 1 5 to 18 inches. This shell, in possessing the same general characters, 

 may be considered by some as an extreme variety of Am. coronatus, 

 Bruguiere ; it varies considerably in the size of the umbilicus and 

 number of dorsal ribs ; the latter become obsolete by age in this 

 species, as shown in the adult specimen figured (reduced) by D'Orb. 

 Terr. Jurass. t. 169. f. 5. It also bears considerable resemblance to 

 Am. Banksii, Sow. M. C. tab. 200, and which is also cited by 

 D'Orbigny as a variety of Am. coronatus. This shell, from the Ox- 

 ford clay near Trowbridge, presents, however, a permanent and distinct 

 variety in which the tubercles are more round and prominent and the 

 volutions less angular than in the normal type of Am. coronatus. 



The large knobbed species from the Lewes chalk named A. ^er- 

 amplus by Dr. Mantell (Fossils of the South Downs, p. 200. n. 60 ; 

 Sow. Min. Conch, pi. ccclvii.), also bears a general resemblance to 

 this species. 



The specific name is to commemorate the industry and research of 

 its discoverer. 



Locality. In the Oxford clay near Trowbridge. 



AsTARTE CARiNATA, PhiUips, Gcol. Yorksh. t. 5. f. 3. 



Pl. XXX. fig. 2. 



Ast. testa crassa, gibbosa, ovato-triangulari, subaequilaterali, costis obtusis concen- 

 tricis instructa, interstitiis paulo latioribus ; lunula ovata, profunda ; raargine 

 intus valde crenata. 



Shell ovately trigonal, ventricose, subequilateral, concentrically 

 costated, costse obtusely rounded ; anterior margin rounded, posterior 

 depressed and slightly truncated ; lunule smooth, ovate, deeply im- 

 pressed, inner margin strongly dentated. 



Width rather more than length ; length and thickness equal. 



This species is considered to be identical with the Ast. carinata^ 

 Phillips, Geol. Yorksh. pl. 5. f. 3, although that figure does not 

 well display the general character ; it closely resembles the A. vetula, 

 Philippi (Dunker, Palaeontographica, t. 8. f. 3), from the tertiary beds 

 of Cassel, but that species has the anterior margin more angular, and 

 the lunule distinctly striated. 



The intervening furrows are double the width of the costse, and 

 when carefully examined exhibit faint traces of concentric striae. 



Locality. Abundant in the Kelloway rock near Chippenham and 

 Trowbridge, and the Oxford clay of Weymouth and Yorkshire. 



Numerous casts of another species of Astarte (Pl. XXX. fig. 3) 

 are found in the Kelloway rock near Trowbridge, resembling the one 

 figured by Phillips, Geol. Yorksh. pl. 5. fig. 30. 



