﻿170 BRITISH FOSSIL CEPHALOPODA. 



Ctrtoceras in^eqtjiseptum, Portlock, PI. XX. figs. 5, 5a, 8. 



1843. Phragmoceras injEquiseptum, Portlock, ' Geolog. Eeport,' pi. 28a, fig. 4 a, b, p. 382. 

 1854. Cyrtoceras iNjEquiseptum, Morris, ' Catalogue of Brit. Fossils,' p. 302. 

 1857. „ „ Salter in Murchison's ' Siluria,' Foss. gr. 43, fig. 1. 



Syn. 1843. Phragmoceras Brateri, Portlock, loc. cit, pi. 28b, fig. 3, p. 383. (Not P. Brateri of 



Miinster.) 



— Phragmoceras arcuatum, Portlock, loc. cit., pi. 28a, fig. 5, p. 382. 



— Phragmoceras (?), Portlock, loc. cit., pi. 28b, fig. 4. 



— Cyrtoceras (?), Portlock, loc. cit., pi. 28b, fig. 6. 



* 



Type. — Portlock's type of this species is a poor specimen ; his P. Brateri is 

 better preserved, but as that cannot be used it can only supply the description of 

 the species, and cannot serve as the type. The figured specimen is flattened in 

 on one side, and thus is out of shape, but the section must have been elliptical or 

 oval, with the curvature in the plane of the longer axis. The inner side is nearly 

 straight, but the outside has a mean radius of curvature of 1\ inches. The rate of 

 increase of the long diameter is about 1 in 3. No surface is seen, but the body- 

 chamber, about 10 lines long, is terminated by an aperture with a sigmoid boun- 

 dary, and parallel to this are seen at least two thickenings of the shell distant 5 

 and 7 lines further back. There is a slight contraction towards the aperture, but 

 not beyond what is common in Cyrtocerata. The septal surface is not seen. The 

 distance of the septa seems variable, one or two of those near the body-chamber 

 especially being of half size ; but this is not an uncommon feature in many species. 

 The mean distance is j% the l° n g diameter. The sutures are very slightly concave 

 and a little oblique, rising highest on the concave side of the shell. The siphuncle 

 is not properly seen, but it may be internal. Length, 21 in. ; greatest breadth, 1^ in. 

 From the Bala Beds of Desertcreat. In the Museum of Practical Greology. 



General Description. — The Cyrtocerata in the Desertcreat schists seem to 

 have been subject to pressure in every direction, and accordingly the fossils are 

 contorted into a variety of shapes ; but amongst all those described by Portlock 

 under the titles Phragmoceras incequiseptum, P. Brateri, and P. arcuatum, only one 

 species seems to be represented. The least contorted seems to be that called 

 P. Brateri. The section is elliptic (fig. 5a), the long diameter in the plane of 

 curvature, though in contorted examples it is not so. The long diameter may 

 have any ratio to the short less than 2 to 1. The curvature is seen both on 

 concave and convex sides, the radius of the latter being 2-^ inches. The mean 

 rate of increase of the long diameter is 1 in 5. No surface is seen in the speci- 

 men called P. Brateri, but an example in the Dublin Museum from the same 

 locality shows the surface beautifully covered by fine upward imbrications 6 per line, 

 with intermediate ones on the back. These run sigmoidally, the chief concavity 



