48 DEVONIAN FAUNA. 



G. ZincJceni, F. A. Romer/ as given by Barrois,^ has a less incurved and 

 rounded apex, and a much more rapidly increasing whorl. 



2. Sub-genus — Oethonychia, Eall^ 1843. 

 1. ORTHONycHiA ROTUNDA, u. sp. Plate V, figs. 19, 19 a. 



Description. — Shell rather large, elevated, campanulate, not involute. Apical 

 extremity small, bent forward ; the perpendicular from the apex to the plane of 

 the mouth falling within the aperture at one-third of the diameter from its front or 

 inner side. Whorl very rapidly expanding, indented by four indistinct shallow 

 depressions, which run from near the apex to the corners of the mouth. Mouth 

 very wide, expanding, sub-quadrate, considerably wider than long, with a rather 

 undulating margin, which is lobed by the indistinct concavities at the corners. 

 Surface apparently rather irregular, and covered with coarse undulating growth- 

 lines. 



Size. — Height 24 mm. ; width across mouth 26 mm., from mouth to apex 

 15 mm. 



Locality. — A single specimen from Pilton is in the Porter Collection. 



BemarJcs. — This fossil, while approaching Orthonychia quadrangularis, mihi,^ 

 from South Devon, appears to differ specifically by having a more central and 

 recurved apex, a more oblique inner side, a rougher surface marked with undulating 

 growth-lines, and a less quadrate mouth, which is undulated by several concavities 

 round the margins. The apex itself is defective both in the mould and cast of our 

 specimen. 



Affinities. — It approaches Platyceras duhium, Barrels, "^ but seems to differ in 

 being less transverse and less botryoidal, and in having a recurved apex. 



2. Orthonychia acuta, F. A. Bonier, sp. Plate V, figs. 20, 21 ; and Plate VI, 



figs. 1, 1 a, 2, 2 a. 



1855. ACEOCULIA ACUTA, F. A. Burner. Beitr. Harzgeb., pt. 3, p. 6, pi. ii, 



fig. 11. 

 1855. — BiscHOFii, F. A. Bomer. Ibid., pt. 3, p. 6, pi. ii, fig. 10. 



1 184.3, F. A. Eomer, ' Verst. Harzgeb.,' p. 17, pi. vii, fig. 4. 



2 1889, Barrois, ' Mem. Soc. Geo). Nord,' vol. iii, p. 197, pi. xiii, figs. 6— 6c. 



3 1891, Wliidborne, ' Devon. Faun.,' vol. i, p. 223, pi. xxi, figs. 8— 8i. 



* 1889, Barrois, ' Mem. Soc. Geol. Nord,' vol. iii, p. 191, pi. xiii, figs. 1 a, h. 



