132 PROCEEDINGS OE THE MALACOLOGTCAL SOCIETY. 



(=Avicula), but might probably be more correctly regarded under 

 Pterinea, on account of their rectilinear contour, both the anterior 

 and posterior sides being nearly vertical. The dorsal region is bounded 

 by a straight hinge-line, which is produced posteriorly, whilst the body 

 of the shell is convex and oblique. A rounded anterior aliform pro- 

 longation is present, the posterior area constituting a normal expansion, 

 which is excavated at the margin. Surface with indication of con- 

 centric striae of growth. These specimens are related to Avicula, sp. ? 

 of Escher von Linth (Geol. Bernerk. Vorarlberg, 1853, p. 1, pi. iv, 

 fig. 32), from the Muschelkalk of the Austrian Tyrol, but differ in 

 possessing an extended posterior angle. 



Dimensions. — Height 20, length 22 mm. (= Fig. 4). 



3. Gervillia inflata, Schafhautl. PI. XII, Fig. 6. 



Gervillia inflata, Schafhautl: Geog. Unters. Siidbayerischen Alpengeb., 

 1851, pp. 134, 145, pi. xxii, fig. 30. Giimbel : Geologie 

 von Bayern, vol. i (1886), p. 695, woodcut fig. 6. 



A very perfect mould of a left valve of this species has been injured 

 in the urnbonal region during the process of reduction, through the 

 friable nature of the sandstone. Fortunately, before the accident 

 an excellent wax impression was taken, giving very clearly all the 

 details of the shell. It may be referred undoubtedly to this species, 

 as interpreted by Giimbel's figure quoted above. The body of the 

 shell is oblique, tumid, and elongate, with a short rounded anterior 

 auricle. The hinge -line is straight and below the urnbonal region, 

 whilst the posterior expansion is moderately excavated on the outer 

 margin. A series of concentric growth-lines ornament the surface. 



Dimensions. — Height (from anterior expansion to extreme ventral 

 edge) 50, length (from posterior wing extremity to anterior margin 

 of auricle) 37 mm. 



Distribution. — This species is characteristic of the Rhsetic (Kossen- 

 beds) of the Alps, etc. 



4. Pteroperna Malatensis, n.sp. PI. XII, Fig. 7. 



This is represented by a natural mould of a left valve, from which 

 a good impression has been produced in wax. The specimen indicates 

 an ovately oblique, convex, and narrow shell, with a very short and 

 rounded anterior wing. The hinge is straight and moderately long, 

 situated below the urnbonal region of the shell, and supports a 

 prominent aliform expansion. The posterior side of the body of the 

 shell is elevated and abrupt. The surface shows strong concentric 

 growth-lines. The specimen appears to be a new form, for which 

 the above name is proposed, probably related to some of the Lower 

 Oolite species of this genus described by Morris & Lycett, Deslong- 

 champs, etc. 



Pteroperna was established by Morris & Lycett in 1853 for Gervillia 

 costatida, Deslongchamps, and other Jurassic species, which show 

 affinities with the older genus Pterinea and the more modern Pteria. 



