﻿BRITISH FOSSIL CEPHALOPODA. 79 



DESCRIPTION OF THE SPECIES. 



Suborder NAUTILOIDEA. 



Group I. Conici. 



Genus Orthoceras. 



Group I. Brevicones. 

 1. Orthoceras Barbandei, Salter, PI. XYIII. figs. 10, 11, 12 ; PI. XIX. figs. 4, 4a. 



1851. Orthoceras Barrandei, Salter, 'Quart. Joum. Geol. Soc.' toI. vii. p. 137. 

 Syn. Gomphoceras liratum, Salter, ' Carat), and Sihrr. Fossils,' p. 174. 

 Query, Cyrtoceras ^mdlus, Barrande, ' Syst. Sil. de Boheme,' pi. 240, figs. 7-10. 



Type. — This has not been found. From the figure and description, the specimen 

 appears to be flattened, and then has an apical angle of 40°. It is represented as 

 commencing with a point, and one side is rather curved while the other is straight. 

 The body-chamber has a length equal to its own basal diameter ; the aperture is 

 simple. The ornaments are oblique lines of growth, about three per line. The septa 

 are distant one-sixth the diameter, and are parallel to the ornaments. The greatest 

 diameter is ten lines, and the length twenty lines. From the Llandovery Beds ; 

 Mullock. 



General Description. — The type specimen not being available, and yet the species 

 being a well-marked one, I was for a long time surprised that no representative was 

 forthcoming in any collection, till a comparison of the shell called Gomphoceras 

 liratum, in the Woodwardian Museum (PL XVIII. fig. 10), with Salter's description, 

 showed that they must be identical. The section is doubtful, unless the specimen 

 (fig. 12), subsequently referred to, really belongs here, in which case it was elliptic, 

 the axes being in the ratio of 12 to 11. The rate of increase is about 4 in 7 on the 

 whole shell ; but it is much less in the body-chamber than in the septal portion, which 

 gives the shell a vase-like appearance, and has led to its being placed in the genus 

 Gomphoceras. The body-chamber has a length equal to its diameter (fig. 10), and 

 the aperture is simple and undulating (fig. 11). The surface is ornamented with 

 fine lines nearly parallel to the septa, but slightly curving away from the aperture. 

 In the septal portion these are close together, four per line ; but on the body-chamber 

 they are only half as numerous, and become much stronger near the aperture. The 

 septa are direct ; and though in fig. 11 they appear to undulate, this may be due to 

 contortion. They are very close, not more than a line apart. In one example, not 



