GYROCERAS. 93 



so that it is difficult to recognise the species from fragments without the help of the 

 perfect shell. At first the markings are fine, and there are no nodes ; but, as it 

 grows, the surface-ornament becomes coarse, and the nodes appear even on the under 

 shell. These again become less conspicuous near the aperture of the mature shell. 

 The character of the coiling is peculiar, the tangent planes of the opposite ven- 

 tral areas being oblique but parallel, so that the coil looks distorted. This 

 appearance is not, I believe, induced by compression, but is natural. 



Affinities. — It is distinguished from G. tredecimale by its greater asymmetry and 

 by the number of its longitudinal ribs, and from the other Devonshire species by 

 the obliquity of its transverse ridges. 



G. paucinoditm, Hall/ is a narrower shell, with a circular spire in which the 

 whorls never touch. Its nodes are fewer, and it has no signs of any minor 

 ornamentation. 



2. Gteoceras asymmeteioum, n. sp. PI. VIII, figs. 4, 4 a. 



Description. — Shell large, highly ornamented, tapering rather slowly. Sections 

 irregularly circular or elliptic in different parts. Rate of tapering about 2 in 5. 

 Coil of spire apparently rising above the plane of the whorls. Surface marked with 

 few prominent, low, rounded, longitudinal ribs, which become smaller and much 

 closer on the dorsal side, and slightly alternate ; the alternating rib upon the 

 centre of the ventral area and those on the two shoulders being obsolete and so 

 giving rise to a central and two lateral flat surfaces. Ribs nodulated by very 

 distant oblique transverse ridges, which do not appear to be foliaceous. 



Size of fragmentary specimen 77 mm. long, and 35 mm. in greatest diameter of 

 the chamber. 



Locality. — Wolborough. Two specimens are in Mr. Vicary's Collection, one 

 of which is very fine, though only a fragment. 



Bemarhs. — For a long time I considered this to be a specimen of G. ornatum, 

 Phillips (not Goldfuss) ; but when the latter species became better known to me 

 it became apparent that the present fossil differed considerably from it. The 

 transverse ridges are much more distant and oblique, and they do not appear to 

 have such a tendency to become foliaceous ; the shell also appears to taper some- 

 what more rapidly, and the coil seems to be more spirally elevated. The section 

 also is more evenly rounded at the sides. Until, however, more perfect specimens 

 are known, it will not be possible to give its full characters, and hence it is 

 possible that some unexpected relationship may be discovered. 



' 1879, Hall, ' Pal. N. Y.,' vol. v, pt. 2, p. 380, pi. liv, figs. 1—4. 



