THE CORALLIAN ROCKS OF ENGLAND. 393 



where they rise each to a tubercle, whence run bifurcating ribs 

 to 38 smaller tubercles, which stand out boldly from the front. 

 Front crenated by largish teeth, connected with the side -tubercles by 

 almost obscure, not very oblique riblets ; diameter 2^ inches. In 

 the young state, which appears slightly more evolute, the ribs are 

 undeveloped, and the whorls have only scattered tubercles. This 

 differs principally from A. vertebraUs and others (1) by being more 

 evolute, (2) by being more uniformly convex, (3) by its tubercles 

 being more marked, (4) by its straighter and thicker ribs, (5) by 

 the more complete separation of the keel, (6) by the teeth on the 

 keel being less oblique. 



In the limestones referred to the age of the Coral Rag at Sike 

 Gate, near Cawton, Yorkshire ; also at Culham, Oxfordshire. 



Chemnitzia langtonensis, spec. nov. PI. XITI. fig. 3. 



Although this is an incomplete and unique specimen, its orna- 

 ments are so distinct and remarkable that it can be confounded 

 with no other Chemnitzia. 



It also possesses a remarkable callosity on the inner lip, which 

 ought perhaps to separate it from this genus. 



Spiral angle 19°, angle of suture 130°. Total length b\ inches 

 (estimated) ; last whorl 2 inches long, double the next whorl ; 

 whorls only moderately convex, least so in the upper part ; suture 

 not deep, but rather abrupt ; ornaments irregular, undulating 

 risings parallel to the length of the shell, numerous, and close 

 together. 



In the Coral Rag of Langton Wold, Yorkshire. 



Chemnitzia pseudolimbata, spec. nov. PI. XIII. fig. 4. 



Spiral angle 14°, angle of suture 115°. Total length 2| inches; 

 last whorl f inch, not quite twice the next ; whorls moderately 

 convex, sutures ill defined. Ornaments, numerous fine transverse 

 curved ribs, the concavity towards the aperture. 



The nearest ally to this seems to be C. limbata, Contejean ; but 

 the present species is not limbate, and the ornaments are not 

 sigmoid. 



In the Ironstone of Abbotsbury. 



Chemnitzia ferruginea, spec. nov. PI. XIII. figs. 5, 5 a. 



Spiral angle 26°; angle of suture 110°. Total length 1 inch; 

 last whorl more than ^ the length, twice the next ; whorls mode- 

 rately inflated, each with 11-12 transverse elevated ribs, curved 

 towards the aperture at the top ; the ribs and interspaces between 

 them. covered with fine longitudinal striae; mouth rather oval, 

 beautifully shown in the specimen communicated by J. F. Walker, 

 Esq., F.G.S. &c. (fig. 5 a). 



In the Ironstone of Abbotsbury. (Woodwardian collection.) 

 The Woodwardian specimen is eminently chemnitzioid ; but Mr. 

 Walker's is more inflated, and is like a Scalaria. The ornaments 

 are the same in both. It is possible, however, they may be distinct. 



