from North CormcaU. 155 



Orthoceras cf. HEECYNicuM, E. Kajser. (PI. V, Figs. 6a, 66.) 



Orthoceras hercynicum, E. Kayser: Abhandl. zur geolog. Specialkarte v. Preussen, 

 etc., Bd. ii, Heft 4 (1878), p. 72, pi. x, figs. 7, 8, 11 ; pi. xi, fig. 3 (?). 



Among the specimens submitted to me by Mr. Howard Fox there 

 are several examples of the genus Orthoceras. The most nearly 

 perfect specimen is represented in PI. V, Figs. 6a, 66. It is 

 a crushed internal cast about 200 mm. in length, of which the body- 

 chamber occupies about 55 mm. The rate of tapering is about 1 in 5, 

 the greatest width at the aperture being about 40 mm., and at the 

 last septum about 28 mm. In its crushed condition the depth of th& 

 chambers is about one-third of their width. The siphuncle is^ 

 slightly excentric (see Fig. 66). Parallel to, and at about 8 mm. 

 below the aperture on the side of the body-chamber opposite to that 

 ■which is figured, there is a shallow constriction about 6 mm. wide. 

 There are no remains of the test : the surface of the cast is smooth. 

 The specimen, though evidently much compressed during fossilization^ 

 probably originally had an elliptical cross-section. The septa are 

 rather oblique, but being nearly parallel to the aperture this obliquity 

 may be due in great measure to crushing. On the whole the 

 specimen seems to be compai'able with such a form as Ortlioceras 

 hercynicum, described by Kayser from the limestone at Hasselfelde 

 in the Hartz belonging to the lower part of the Middle Devonian, 

 or with the form which Kayser figures and describes as Orthoceras sp. 

 (op. cit., p. 72, pi. xi, fig. 1), from the same horizon and locality. 



A septated fragment, about 45 ram. long, is possibly referable to 

 this same species. 



Orthoceras cf. commutatum, C. G. Giebel. 



(See Text-figui-es, p. 156, Figs. 1, la.) 



Orthoceras comnmtatum, C. G. Giebel: Fauna der Vorwelt, Bd. iii (1S52), p. 233.' 



Another Orthoceras indicating a different species is represented in 

 the accompanying figures (Figs. 1, la). It is flattened, slowly tapering, 

 and about 92 mm. long ; the ventro-dorsal and transverse diameters 

 in its present crushed state being 25 and 51, and 23 and 40 mm. 

 respectively. It consists of the internal casts of three chambers, 

 and of part of a fourth, the anterior one being imperfect; the septa 

 are about 21 mm. apart. The siphuncle is not clearly shown, but 

 at the posterior end of the specimen there appears to be a faint 

 indication in a slightly excentric position of something which may 

 have been the siphuncle. There is also a depression at the anterior 

 end, but this seems to be the impression of another organism. The 

 surface of the cast is smooth ; there are no traces of any sculpture. 

 This specimen, characterized by its deep chambers and slowly 

 tapering shell, appears to be related to the Devonian form which 

 Kayser has figured (loc. cit., pi. x, figs. 1-3 ; pi. xi, figs. 4, 8) as 

 Orthoceras commutatum, Giebel, and recorded from the limestone at 



' This is the species which was described as Orthoceras longicameratum by Foord 

 (Cat. Foss. Ceph. Brit. Mus., pt. i, 1888, p. 80), but this name being preoccupied 

 Foord altered it to 0. nassoviense (ibid., Corrigenda and Addenda, p. xxxi). The 

 species, however, is evidently the same as that for which Giebel had already proposed 

 the name 0. commutation. 



