ORTHOCERAS. 121 



or sub-elliptical in cross-section. Septa concave, usually horizontal, sometimes a 

 little oblique, widely separated as a rule. Siphuncle usually slender, cylindrical, 

 central, sub-central, or eccentric. Body-chamber large, of variable length. 

 Aperture simple." It extends from the Cambrian to the Trias, and contains, 

 according to Barrande, 1146 species. Its greatest development is in the Silurian 

 System, but the Devonian forms are very numerous. 



Barrande divides the genus into two sections, Brevicones and Longlcones. 

 The former is represented in these strata by a single species, 0. rapiforme, 

 Sandberger. The Longicone species are much more numerous. Phillips 

 recorded three from these beds, but it will be seen that we have now reason to 

 increase the total number in the two sections to sixteen (or fifteen and one variety). 

 Some of these fossils are in a beautiful state of preservation, but they are almost 

 all fragmentary, and owing to the minute character of many of the specific 

 differences in this genus, and their liability to change with the age of the shell, 

 there is often much difficulty in discriminating the species. For the most part 

 the shells are rare, but one or two, as 0. hibicinella, 0. laterale, and 0. Vicarii^ 

 appear to have been fairly abundant. 



1. Oethoceeas eapiforme, Sandberger. PI. XIII, figs. 14, 14 a, 15, 15 a. 



1852 ? Okthoceeas eapifoeme, Sandberger. Verst. Ehein. Nassau, p. 167, pi. xix, 



figs. 4, 4 a. 

 1850, — EAPJsrOEME, F. A. Bomer. Beitrage, pt. 1, p. IG, pi. iii, 



figs. 18, IS a. 

 1858. — EAPIFOEME, Selmersen and Pacht. In Baer's Beitr. Euss. 



Beich., vol. xxi, p. 85, pi. iii, fig. 5. 



Description. — Shell straight, short, conoidal. Section almost circular. 

 Siphuncle central. Rate of tapering, 3 in 7. Septa apparently narrow and 

 rather oblique. Surface covered with fine, regular, rather distinct, impressed 

 striae, with finer imbrications. Apex very small. 



Size. — Length, 58 mm., greatest width, 21 mm. 



Locality. — "Wolborough. A fine but worn specimen is in the Torquay 

 Museum ; another, rather smaller, in the Museum of Practical Greology (Godwin- 

 Austen Collection) ; and two others, which are small and poor, in Mr. Vicary's 

 cabinet. 



Remarks. — These specimens are definitely distinguished from the other 

 accompanying species by the large angle of their cone, but unfortunately they do 

 not preserve many of their specific characters. The specimen in the Torquay 



