1857.] WRIGHT LIAS FOSSILS FROM SKYE. 29 



Ammonites Davcei, Sowerby, 1822. 



Ammonites Davcei, Sowerby, Mineral Conchology, t. 350 ; d'Orb. 

 Paleontol. Francaise, Terr. Jurassiques, t. 81, 1844; Quenstedt, 

 Cephalopoda, t. 5. f. 6. 



The only specimen of this Ammonite contained in the collection 

 has the shell tolerably well preserved ; the fine irregular layers of 

 growth which impart a wrinkled appearance to the whorls, with the 

 few distinct tubercles, from ten to twelve in a whorl, placed on its 

 outer border, serve to distinguish this species from Amm. armatus, 

 Sow., and Amm. subarmatus, Sow., with which it might be con- 

 founded. 



Ammonites Davcei, Sow., is found at Charmouth in the upper 

 region of the Middle Lias ; in Gloucestershire I have a specimen 

 collected from a bank of clay above the zone of Ammonites ibex, 

 Quenst. {A. Boblayei, d'Orb.) and Amm. bipunctatus, Roem. (A. 

 Valdani, d'Orb.). In Swabia Dr. Oppel found it in this horizon 

 near Boll, at Fiizen and at Randen. D'Orbigny gives many localities 

 for this species in France, where it is proper to the Middle Lias, 

 "bien au-dessous de la Gryphcea cymbium. ,> 



Trochus imbricatus, Sowerby, 1819. 



Trochus imbricatus, Sow. Mineral Conchology, t. 272. f. 3, 4. 



The only examples of this species are two interior moulds, from 

 which the shell is entirely denuded ; the whorls are rather more 

 convex than the type-forms of this fossil from the Middle Lias Clays 

 near Cheltenham, from whence Sowerby' s specimens were obtained. 



Pholadomya ambigua, Sowerby, 1819. 



Pholadomya ambigua, Sowerby, Mineral Conchology, t. 227. 



The two specimens of this shell are small, about 2 inches in length ; 

 but they agree in the form of the mould, the number of the ribs, and 

 the style of the lines of growth, with true forms of this species of 

 the same size found in the Middle Lias, near Cheltenham, in com- 

 pany with Ammonites Henleyi, Sow., Pleurotomaria expansa, Sow., 

 Pecten cequivalvis, Sow., and Modiola scalprum, Sow. 



Pleuromya Scottica, Wright, nov. sp. 



Shell oval, umbos large, prominent, and forming conspicuous re- 

 curved projections, the points of which extend to the anterior border; 

 sides much inflated below the umbos, and marked with numerous 

 longitudinal elevations and depressions ; the moulds are so much 

 distorted that neither their number nor the true form of the shell 

 can be ascertained. 



This species resembles PI. unioides, Roem., in the longitudinal ele- 

 vations on the shell, but differs from it in having the curvature of 

 the umbos level with the anterior border, instead of at the anterior 

 third, as in PI. unioides. The forward position of the umbos like- 

 wise distinguishes it from PI. rostrata, Agass. 



