CYRTOCERAS. 107 



curvature and rate of tapering being very much less, by its transverse frills being, 

 as far as can be judged in its state of preservation, more crenulated and mem. 

 branaceous, and by their increasing in distance and changing in character much 

 less rapidly. Thus it appears evidently not to be allied to that shell. 



In the second place it shows much similarity to G. fimhriatum, Phillips. 

 Compared with that species, however, its curvature appears decidedly greater 

 its transverse frills are much further apart and less undulating, and its increase in 

 size seems more rapid. Hence it does not seem possible to unite it with that 

 species. 



I am therefore obliged at present to treat it as a distinct form, although 

 when more complete specimens are found they may prove that it ought to be 

 reunited to some other species. It is to be noted that there are faint indications 

 of a secondary series of transverse bands intermediate to the primary frills, and 

 not foliaceous, and this character I have not noticed in any other species. 



4. Cyetoceras, n. sp. PI. XII, fig. 4. 



Description. — Shell small, decidedly recurved, very rapidly tapering. Ventral 

 outline convex, dorsal outline very concave near the apex, but becoming straight 

 near the body -chamber. Septa very concave, set obliquely. Siphuncle near the 

 ventral margin. Surface unknown. 



Size. — A specimen of the septal part of the shell, 27 mm. in length, measures 

 about 21 in ventro-dorsal, and 20 in lateral diameter at the upper end, and 8 mm. 

 in diameter at the apical end. 



Localiti/. — Two defective specimens from Wolborough are in the Museum of 

 Practical Geology. 



Bemarks. — This little species is evidently a brevicone Gyrtoceras, but its 

 remains are too scanty to admit a very certain identification. There is, however, 

 no other species from our Devonshire localities which is at all similar to it ; nor 

 have I met with any foreign species which appears to correspond. 



Affinities. — Gyrtoceras indomitum, Barrande,^ while agreeing with the smaller 

 of the two specimens in the Museum of Practical Geology in general shape, differs 

 in having its siphuncle subcentral instead of marginal. G. cornucopia, Sandberger," 

 G. bilineatum, Sandberger,* and C. breve, Sandberger,* are less recurved and more 

 slowly tapering shells, and have more elliptic sections. 



' 1866, Barrande, ' Syst. Sil. Boheme,' vol. ii, p. 700, pi. cl.xii, figs. 1—14, Et. E. 



2 1852 ? Sandberger, ' Verst. Rhein. Nassau,' p. 142, pi. xiii, figs. 4 a, b. 



* Ibid., p. 143, pi. xiv, figs. 2 a—f. 



* Ibid., p. 143, pi. XV, figs. 5 a — c. 



