TENTACULITES. 37 



Description. — Test conical, rather elongate, regular, slightly oblique. Section 

 apparently circular. Rate of increase 1 in 3. Surface divided by about twenty- 

 two sharp, raised, slightly irregular annuli, which are not quite parallel near the 

 aperture ; with slightly concave, wide interspaces, which are finely and obliquely 

 striated from right to left (thus / / / ) when viewed with the apex at the bottom. 



Size. — Height 7 mm., width at aperture 2-5 mm. 



Locality. — A single specimen, mould and cast, from Top Orchard is in the 

 Barnstaple AthensBum. 



Bemarlcs. — The specimen is somewhat crushed, so that it is not possible to be 

 certain that it was circular in section ; and from the roughness and decomposition 

 of the matrix the oblique striation can only be seen with great difficulty. 



It is evidently a Tentaculite, and so closely approaches Tentaculites conicus, 

 F. A.. Romer, of the Wissenbach Slates, that I think it may probably be referable 

 to that species. The only difierences I can see are that the German fossil is slightly 

 more elongate, increasing at the rate of two in seven instead of two in six, and 

 that the striation is not seen in the figures. The latter is, however, so very minute 

 that it might very well not have been noticed, and in specimens from Wissenbach in 

 the British Museum, Mr. Crick and I discovered a similar striation, though it seemed 

 direct rather than oblique. The former difference is probably due to the English 

 shell being a little flattened out. I therefore have little doubt that they are 

 identical. 



Affinities. — This is distinguished from Tentaculites tentacularis, Phillips, sp., 

 by its very much lower rate of tapering. 



T. subconicus, Geinitz,^ is much narrower, increasing at the rate of two in 

 eleven, but Geinitz hesitates whether to regard it as more than a variety. He 

 states^ that T. anmdatus, Schlotheim,^ is very much larger, and that Schlotheim's. 

 fig. 8 a is Silurian, but fig. 8 6 is Devonian. 



Orthoceras Ausavense, Steininger, is considerably larger and more elongate,. 

 but is otherwise very similar in general appearance. 



T. durus, Ludwig,* seems narrower and larger. 



T. acuarius, Richter,^ as given by Kayser,® has fewer annuli, and the striae are- 

 longitudinal, not oblique. 



1 1853, Geinitz, ' Verst. Grauwack. Saschen,' pt. 2, p. 73, pi. xix, fig. 15. 



2 Ibid., p. 73. 



3 1820, Schlotheim, ' Petrefact.,' p. 877, pi. xxix, fig. 8 a. 



* 1864, Ludwig, ' Palseontograpli.,' vol. xi, p. 818, pi. 1, figs. 8 a, b. 



^ 1854, Eichter, ' Zeitscli. Deutsch. Geol. Gesell.,' vol. vi, p. 285, pi. iii, figs. 3—9. 



* 1878, Kayser, ' Abhandl. Geol. S|;ecialk. Preuss.,' Band ii, pt. 4, p. 112, pi. xxxi, fi(^s. 1 ,3.. 



