GONIATITES. 75 



IL GoNiATiTES, sp. PL VI, figs. 14, 14(1, 14 &. 



Description. — Shell small, almost involute, discoidal, flattish. Umbilicus 

 minute, deep, aciculate. Sides of the whorls flattened obliquely, and meeting in a 

 narrow rounded back. Suture-line with a very small triangular central lobe (?), 

 very oblique central saddles, large bluntly triangular lateral lobes which are very 

 much in advance of the central lobe, and lateral saddles of a similar bluntly 

 triangular shape, but smaller than the lobes. 



Size. — 15 mm. in height, 7 mm. in depth. 



Locality. — Wolborough. A single specimen in the Museum of Practical 

 Geology. 



Remarks. — This beautiful little specimen appears to represent a shell which is, 

 as far as I can see, unlike any of the accompanying species. I at first supposed 

 the shells depicted on PI. VI, figs. 13 and 15, to belong to the same species, but the 

 former appears on closer examination to be an aberrant example of C. psittacinus, 

 and the present form differs from it in the more arched character of its lobes, the 

 retrogression of the central lobe, and in its greater flatness, while it is distinguished 

 from fig. 15 by the different contour of the suture-line and the absence in it of a 

 broad central convexity. 



The surface of the specimen now under review is marked by raised lines which 

 are misleading, as they are neither the external ornament nor the suture-line of the 

 existing whorl, but the springing of the walls of the chambers of a vanished whorl. 

 It was only when I recognised this fact that I was enabled to understand it, and 

 to separate it from the fossils above mentioned. The suture-line is given by the 

 termination of the specimen which has separated along the walls of one of the 

 chambers. 



Affinities. — G. retrorsus, von Buch,^ is clearly distinct on account of the larger 

 umbilicus, and because the character of its ornamentation would probably imply a 

 differently shaped suture-line. That species has gone through many fluctuations. 

 Beyrich's figure^ much more nearly approaches our fig. 13, but is quite different 

 from G. psitticanus, to which that specimen is found to belong ; while the present 

 fossil seems to differ from it by the rapid increase of its whorls, the greater sharp- 

 ness of its lobes and saddles, and the backwardness of the central lobe. On the 

 other hand, as interpreted by d'Archiac and de Verneuil,^ G. retrorsus is very unlike, 

 having a large umbilicus and a more acute back, but these authors give an 

 indistinct figure of a variety of their species, which they assert to be the shell 

 originally described by Bey rich. 



1 1832, von Buch, ' Uber Amni. und Gon.,' p. 49, pi. ii, fig. 13. 



2 1837, Beyrich, ' Beitr. Eheiu. Ubergangsg.,' p. 30, pi. i, figs. 10 a — c. 



3 1842, D'Arcb. and de Vern., ' Geol. Trans.,' ser. 2, vol. vi, pt. 2, p. 338, pi. xxv, figs. 3—5. 



