GYROCERAS. 99 



it, G. costatum, giving a baseless priority to a manuscript name. There can, 

 however, be no doubt of the distinctness of the two species, if from no other 

 reason, from the very different rate of increase of the whorls, as may be seen in 

 the fine series of each in the British Museum. 



If G. tentaeulatum, Miinster sp., should prove identical, that name would of 

 course have to supplant that of G. Eifelense, but I have not at present adopted it, as 

 the question requires further elucidation before coming to an ultimate conclusion. 



6. Gyeoceras Crickii, n. sp. PI. X, fig. 10. 



Description. — Shell small, much arched, very rapidly increasing. Surface 

 marked with about thirty distant, rounded, longitudinal ribs, separated by broad 

 interspaces, that over the siphuncular area being slightly broader than the rest ; 

 the whole crossed by very numerous fine, regular, thread-like, transverse lines, 

 which are convex to the apex upon the interspaces. 



Size. — The fragment, which is about 31 mm. in length, measures 18 mm. in 

 ventro-dorsal and 13 mm. in lateral diameter at its upper end. 



Locality. — Wolborough. A single defective but beautifully preserved speci- 

 men of the chambered portion of the shell is in the Museum of Practical Geology. 



Remarks. — I felt some doubt as to the way in which this beautiful little 

 specimen should be treated, chiefly on account of its fragmentary condition. It 

 appears, however, to me that even the small portion that remains of it proves that 

 it must be distinct from either G. Eifelense or G. tredecimale, for it shows 

 no signs of any major transverse ridges, and the minor transverse marks are 

 much more regular and definite than in either of the former species. It would 

 appear, moreover, to be more circular in section, and more rapid in its rate of 

 tapering. 



I have much pleasure in naming this species after Mr. Crick, who has given 

 me much kind help in the examination of the Cephalopods in the British Museum. 



7. Gyrocbeas armatum, Phillips^ sp. PI. XII, figs. 1, 1 a. 



1841. Ctetocebas aematum, Phil. Pal. Foss., p. 118, pi. xlviii, fig. 225. 

 1841. — NAUTiLOiDETJM, Phil. Ibid., p. 116, pi. xlvi, fig. 220. 



1888. — AEMATUM, Etheridge. Foss. Brit., vol. i. Pal., p. 167. 



1888. — NAUTiLoiDEXJM, Etheridge. Ibid., vol. i. Pal., p. 167. 



Description. — Shell large, flattened, almost or quite symmetrical, moderately 

 arched about the body-chamber, and very rapidly reflexed in the lower part of the 



