ORTHOCERAS. 131 



body-wliorl, the ribs and strige are as prominent and definite as in any of the 

 smaller specimens. 



Affinities. — Of the Devonshire shells described by Phillips, Orthoceras Uneolatum, 

 Phil.,^ is the species which comes nearest to the present fossil. This differs appa- 

 rently in its rings being much further apart and more definitely oblique, and in 

 the smaller ornamentation being gently undulating ; the siphuncle appears to 

 occupy a similar position. The specimen, however, figured in the " Palgeozoic 

 Fossils " is evidently a poor and distorted fragment, and is identified by Phillips 

 with a Yorkshire shell,^ 0. annulatum, Phillips (not Sow.), which strongly 

 emphasises these distinctions. 



0. tentaculare, Phil.,^ if it be an Orthoceras, may be distinguished from the 

 present form by its curved shape, and by the greater size and prominence of 

 its rings. 



In 0. striolatum, H. von Meyer,* from the Posidonomy en- S chief er, the rings are 

 altogether closer, finer, and more numerous. 



0. Dannenbergi, d'Arch and de Vern.,^ whicb, according to Mr. Foord,^ is the 

 same as 0. undato-lineolatum, Sandb.,^ appears to be decidedly different, as its 

 rings are undulating and oblique to the septa, and are crossed and imbricated by 

 the finer strise. 



0. pulchellum, F. A. Rom.,^ differs from it in having a very elliptic section, a 

 marginal siphuncle, four rings instead of three on each segment, and in its 

 segments being three, and not four, times as wide as they are deep. 



0. inseqidstriatum, F. A. Romer,^ from the Culm of Grund, seems a very 

 nearly allied form, which may, however, be distinguished by the rings being much 

 more numerous and minute, and arranged in an alternating series, and by the 

 chambers being as high as they are wide. 



0. per annulatum, Portlock,^" is larger, more conical, and has more rugose and 

 rounded annulations. 



0. elongato-cinctum, Portlock,^^ has the rings finer and closer and is more 

 conoidal. 



1 1841, 'Phil. Pal. Foss.,' p. Ill, pi. xliii, fig. 209. 



2 1836, Phillips, ' Geol. Torks.,' vol. ii, p. 239, pi. xxi, figs. 9, 10. 



3 1841, ' Phil. Pal. Foss.,' p. 112, pi. xliii, fig. 210. 



* 1831, H. von Meyer, 'Nov. Act. Acad. Leop. -Carol.,' vol. xv, pt. 2, p. 59, pi. Ivi, figa. 1 — 12, 

 not pi. Iv ; and 1852 ?, Sandberger, ' Verat. Ehein. Nassau,' p. 165, pi. xix, figs. 3 a, h. 



^ 1842, D'Arch. and de Vern., ' Greol. Trans.,' ser. 2, vol. vi, pt. 2, p. 345, pi. xxxviii, figs. ], 1 



8 1888, Foord, ' Cat. Foss. Ceph. Brit. Mus.,' vol. i, p. 84. 



"> 1852 ?, Sandb., ' Verst. Ehein. Nassau,' p. 163, pi. xviii, figs. 6 a—d. 



8 18r)0, F. A. Eotn., ' Beitr.,' pt. 1, p. 39, pi. vi, fig. 5. 



9 1852, F. A. Eomer, ' Beitr.,' pt. 2, p. 92, pi. xiii, figs. 23 a, b. 



10 1843, Portlock, ' Eep. Geol. Londonderry,' p. 367, pi. xxv, figs. 5, G. 



11 Ibid., p. 372, pi. xxvii, figs. 2 a, b. 



