126 DEVONIAN FAUNA. 



Hall thus defines his genus, giving P. Salamanca, Hall, as an example. It 

 accurately covers the English species. 



1 . PTYCHOPTERIA DAMNONIENSIS, Sowerby, sp. Plate XIII, fig. 14 ; and Plate XIV, 



figs. 913. 



1810. AVICULA DAMNONIENSIS, Soicerly. Geol. Trans., ser. 2, vol. v, pt. 3, pi. liii, 



fig. 22. 



1841. Phillips. Pal. Foss., p. 51, pi. xxiii, figs. 9092. 



1841. CANCELLATA, Phillips. Ibid., p. 49, pi. xxii, fig. 84. 



P 1884. PTEBINEA, cf. DAMNONIENSIS, Clarke. Neues Jahrb. f. Min., Beil.-Band 3, 



p. 372. 

 ? 1884. PTTCHOPTEHTA SALAMANCA, Hall. Pal. N. Y., vol. v, pt. 1, p. 131, pi. xxiii, 



figs. 1720. 



? 1884. SAO, Hall. Ibid., p. 132, pi. xxiii, figs. 16, 23. 



1893. ATICULA DAMNONIENSIS, Collins. Trans. Eoy. G-eol. Soc. Cornwall, vol. xi, 



p. 35. 



Description. Shell rather large, convex, inequivalve, subtrigonal, generally 

 very transverse. Hinge nearly as long as shell, straight. Umbo broad, proximate, 

 situated very anteriorly, curving forward, low in the right valve, prominent and 

 overhanging the hinge in the left valve. Anterior wing small, narrow, sub- 

 triangular, with an obliquely convex margin below, apparently meeting the hinge- 

 margin at an acute angle. Inferior margin very long, oblique, and slightly 

 convex. Postero-inferior corner much produced and very convex. Posterior 

 margin oblique, straight. Hind wing long, triangular, rather broad, convex along 

 its centre, and separated from the body by a strong linear concavity. Surface 

 covered by very numerous, minute, equal, close, rounded ribs, crossed by a few 

 strong growth-ridges, and by very numerous fine, close, rounded threads. Left 

 valve more convex than the right. 



Size. Three specimens measure 23 mm. high by 40 mm. long, and 13 mm. 

 deep ; 14 mm. high by 18 mm. long, and 5 mm. deep ; 32 mm. high by 40 mm. 

 long, and 13 mm. deep. A specimen from West Angle is 47 mm. long. 



Localities. In the Barnstaple Athenaeum are six specimens from Sloly, five 

 from Marwood, one from Kingdon's, Shirwell, and two from Top Orchard. In 

 the Museum of Practical Geology are eighteen from Marwood, one from Baggy, 

 and eight from West Angle Bay, Pembrokeshire; in the Woodwardian Museum, 

 Sowerby's type from Marwood, and six from Barnstaple ; in my Collection one 

 from Pouch Bridge. It crowds the surface of a bed just above the Rh. laticosta 

 bed at Baggy. 



