GONIATITES. 77 



the general run of that species, and is very much decorticated, so that the 

 umbilicus is uncovered, and is probably larger than it originally was. 



Fig. 14, on the other hand, while at first sight very similar to our fossil, is 

 really shown by the lobation to be quite distinct. It wants the body-chamber, 

 and hence the terminal line really gives the suture, which is quite different from 

 that of the present species. 



The character of the suture-line in the present fossil is much obscured by the 

 shell having been broken nearly, but not quite exactly, along it. Supposing the 

 tracing I have given to be a fairly correct representation of it, as I imagine it to be, 

 it will be seen that it is of a somewhat unusual contour and differs very widely from 

 that of G. retrorsus, von Buch, and other species of that group. I have not met 

 with any foreign species which seems to approach the present shell at all nearly, 

 but as the specimen is so defective and obscure I have not ventured to give it a 

 specific name. 



13. GoNiATiTES NuciFOEMis, WJiidbome. PI. VI, figs. 7,7 a, 7 h; and PI. VII, fig. 1, 1 a. 



1889. GrONiATiTEs NUciFOKMis, Whidh. Geol. Mag., dec. 3, vol. vi, p. 29. 



Description. — Shell small, spheroidal, quite involute. Umbilicus minute and 

 very deep ; the edges of the inner whorls hidden by the smallness of the aper- 

 ture. Suture-line very simple, consisting of a bow-shaped line, bent slightly 

 forward over the back. Sides of the whorls flattened dorsally, arching ventrally 

 in a rather deep curve to the broad back, which again is rather flattened. 

 Siphuncle large, situated so close to the median line of the back as to be included 

 in the structure of the shell. Chambers broader than they are high. Walls of 

 chambers concave, simple. Mouth more than half filled by the back of the 

 next whorl. 



Size. — 17 mm. in height, 13 mm. in width, 12 mm. in depth. 



Locality. — Wolborough. There are seven specimens in the Vicary Collection, 

 three or four in the Torquay Museum, two in the Museum of Practical Geology 

 (Godwin- Austen Collection), and one in the British Museum. 



Remarks. — This is an interesting little species, which does not seem, if we may 

 judge from the specimens we have examined, to have been subject to any very 

 great amount of variability. The subquadrate shape of its section, the siphuncle 

 buried in the shell-wall, and the deep aciculate umbilicus are distinctive features. 

 In Mr. Vicary' s largest specimen, which is probably an old or full-grown shell, 

 the depth of the shell seems greater in the vental part than near the umbilicus, so 

 that its profile might perhaps be well described as key-hole shaped. There is in 



