﻿94 BRITISH FOSSIL CEPHALOPODA. 



Orthoceeas subannulare, Miinster, PI. Y. figs. 6, 6a. 



1840. Orthoceratites subannularis, Miinster, ' Beitr.' iii. pi. 19, fig. 3, p. 99. 



1852. Orthoceras subannulatum, M'Coy, ' Pal. Fossils,' p. 320 (part). 

 1866. „ subannulare, Barrande, ' Syst. Sil. de Boheme,' pi. 283, &c, p. 343. 



1873. „ „ Salter, ' Cambrian and Sil. Foss.' p. 159 (not p. 98). 



Not 1843. Orthoceras subannulare, Portlock, ' Geol. Bep.' pi. 25, fig. 78. 



Type. — The figure and description of Munster show that the section is circular, 

 the shell without any curvature, and the rate of increase 1 in. 12. The ornaments 

 are apparently direct rings, flatter and nearer together than in 0. annulatum, at the 

 smaller end about \ and at the larger end -jt the diameter apart ; the whole is finely 

 " striated " transversely when the shell is preserved. The septa have considerable 

 convexity, and the siphuncle is central. Length, 2£ inches ; diameter, § inch. 



General Description. — Although our British fossils agree with Munster 's type, as 

 far as the above characters are concerned, it is rather with the well-illustrated speci- 

 mens of Bohemia that comparison must be made. Only one example shows any 

 section, and in that it has been compressed. The rate of increase is consequently 

 not to be ascertained. The ornaments are feebly-marked rings with narrower inter- 

 spaces, which are direct, as seen, though Barrande describes and figures his as 

 undulating ; they are distant from -^ to \ the flattened diameter. On these rings 

 are a number of parallel riblets, which have a forward imbrication ; they are about 

 six to each ring, and on account of their direction are further apart on the posterior 

 than on the anterior slope. Towards the aperture the rings become irregular and 

 nearly die off, but indications of them may still be seen. No septal characters are 

 perceived in any. Greatest length seen, 1^ inches ; greatest diameter, 1 inch. 



Relations. — I fear there may be some confusion about this species, as Barrande's 

 may not be the same as Miinster's, and the latter may correspond more closely to those 

 I have referred to 0. Duponti. These slightly ribbed species, as their history is learnt 

 from Bohemian examples, change their character in the adult, and are much alike 

 when young ; the distinguishing character of those collected under this name is the 

 fewness and upward imbrication of their riblets, and their undulations are not entirely 

 lost near the aperture. The British examples, however, are very badly preserved, 

 and throw little light on their true nature. However, M'Coy recognised this 

 species as occurring in Britain. It chiefly differs from 0. dulce in the weakness 

 of the ribbing. 



Distribution. — In the Wenlock Shale of Builth (1) and in the Lower Ludlow of 

 Dudley (?) (1) and of Usk (3), and possibly in the Coniston Flags of Coldwell (2). 



Harkness and Nicholson also record this species from the Coniston Beds, Eandy 

 Pike, though the reference may, of course, be to 0. Duponti. 



