632 



SHELLS OF THE WENLOCK SHALE. 



Orthoceras Nummularius, f. 24. Conical ?, smooth ? ; septa very numerous, very convex, -£th their 



diameter apart ; siphuncle large, inflated between the septa to about 3 times its own diameter, 



and ^ the diameter of the septum. Diameter about 4 inches. 



This much resembles O. crassiventris, Wahl. (His. Pet. Suec. p. 30. t. x. f. 3.) but in that 



species the siphuncle fills § rds of the diameter of the chamber, and the septa are not so close. 



Portions of the siphuncle when separated, resemble thick, coarsely made coins. 



Loc. Whitfield Quarry, Tortworth. 

 Orthoceras attenuatum, f. 25. This figure is taken from a drawing supplied by Dr. Lloyd from a 



fine specimen discovered by him, and now in the Ludlow Museum. 



Loc. Banks of the Onny, near Stretford Bridge. 

 Orthoceras virgatum. (See PI. 9. f. 4.) Also Lower Ludlow Rock. 



Loc. Stumps Wood. 



Orthoceras canaliculatum, f. 26. Very gradually tapering, longitudinally furrowed ; furrows about 

 26, shallow, regular; siphuncle central, small. Diameter 1^ inch. 



Somewhat resembling O. Gesneri, Martin, but much less conical and the septa more numerous 

 than in that species. It differs from O. angulatus, Wahl. (His. Pet. Suec. p. 28. t. x. f. 1.), in 

 having a central siphuncle, and in being straight. 

 Loc. Ledbury. 



Orthoceras fimbriatum, f. 20. Gradually tapering, straight and even; ornamented with transverse 

 many arched laminae or flounces, about one line apart, and slight irregular longitudinal furrows 

 and striae ; siphuncle central, large ; septa moderately numerous. The arches of the laminaa 

 terminate in the furrows. Diameter 2 or more inches. 



This differs from the following in the position of the arches of the laminae and in the generally 

 even surface. A specimen in Mr. B. Bright's cabinet contains 3 smaller Orthocerata. 

 Loc. Aston, May Hill; also on the western slopes of the Malverns. 



Orthoceras annulatum. PI. 9. f. 5. (M. C. 133 ; O. undulatus, Hisinger Anteckn. p. 236. t. vii. f. 8 ; 

 Pet. Suec. p. 28. t. x. f. 2. It is not O. nodulosus of Schlotheim which has been referred to O. 

 annulatum of M. C.) Very gently tapering, ornamented with prominent transverse rings, very 

 numerous, transverse, many-arched laminae, and more or less deep longitudinal furrows ; si- 

 phuncle central, large ; septa equal in number to the rings ; the arches of the laminae terminate 

 between the furrows. Diameter li inch. 



The longitudinal furrows in this species are sometimes hardly perceptible, but whenever 

 they can be perceived, the arches of the flounces will be found to spring from the raised spaces 

 between them. 



The figure in Mm. Con. was taken from a fossil in which the furrows were very slight ; our 

 figure is from the more deeply furrowed variety. We have also a specimen in which the fim- 

 briae jare nearly as distant as in the last species, although usually there are four times as many. 

 One individual in Mr. B. Bright's cabinet contains two other small Orthocerata penetrating the 

 chambers; one of them is annulated and has a lateral siphuncle 1 . 



1 The Orthoceras annulatum of the Silurian Rocks is very prevalent in strata of the same age on the continent 

 where it is known as 0. undulatum. This confusion is the more to be regretted, as Mr. Sowerby had previously 

 figured another species from the " Carboniferous Limestone" under the latter name. My readers who may 

 refer to the original figure of 0. annulatum in the Mineral Conchology, will, however, be surprised to see that 

 it differs considerably from the fossil given in this work ; but Mr. J. Sowerby contends that his species is iden- 

 tical with those I have collected, and hence I have retained the name first applied to the fossil. — R. I. M. 



