106 DEVONIAN FAUNA. 



portion, has the frills much finer, and more numerous and regular, and so nearly 

 approaches G. quindecimale that I was almost inclined to class it with that species. 

 The frills, however, would naturally appear closer on the dorsal side. 



(4) The specimen of G. quindecimale figured on PI. X, fig. 1, shows a rapid 

 increase of the coarseness of the ornamentation near the mouth, so as to be like 

 that of No. 3, except that it is not so undulating. 



(5) The specimen of G. quindecimale figured on PI. X, fig. 2, and supposed to 

 be Phillips's type, though very unlike his figure, is clearly the same species as the 

 last (No. 4). In it the ribs are very indistinct, and the frills are very close and 

 prominent, and occasionally one is stronger than the others, so as to divide them 

 into sets as described by Phillips. 



(6) A specimen of G. quindecimale in the Lee Collection in the British Museum 

 is exactly like Phillips's fig. 206 a of that species. 



Affi,nities. — Gyroceras Nereus, Hall,^ has similar transverse undulatjng bands, 

 but diflPers in the absence of longitudinal markings and in its very much greater 

 curvature. 



3. Cyrtooeeas difficile, n. sp. PI. XII, fig. 3, 3 a. 



Description. — Shell elongate, recurved, asymmetrical, slowly tapering, the 

 curvature being greatest near the apex. Upon a cord of 38 mm., subtending the 

 concave side, the greatest curvature is 11 mm. Section circular near the apex, 

 transversely elliptical in the upper part of the shell. Chambers and siphuncle 

 unknown. Surface ornamented with twenty or thirty low indistinct longitudinal 

 ridges, crossed by regular, distant, slightly crenulated membranaceous frills, with 

 a deep convex loop towards the apex on the ventral line, and distant from each 

 other about 4 mm. on the average. 



Size. — The portion of a shell 62 mm. in length measures about 16 mm. and 

 21 mm. on the ventro-dorsal and lateral diameters of its section at the upper end. 



Locality. — Wolborough. A single broken specimen is in Mr. Vicary's Collection. 



Remarks. — The fossil described above has caused me no small perplexity; 

 for, while preserving some clear characters, its true form is obscured partly by 

 fracture and partly by almost indistinguishable matrix. Its ornamentation bears 

 considerable resemblance to two distinct species of shells, but I cannot satisfy 

 myself that it can belong to either, and upon my showing it to Mr. Foord I 

 understood him to have the same difiiculty. 



In the first place it bears very considerable resemblance to a portion of the 

 inner whorl of Gyroceras prseclarum, Whidb., but from that species it differs by its 

 1 1879, Hall, ' Pal. N. Y.,' vol. v, pt. 2, p. 373, pi. li, figs. 4—6. 



