22 GEOLOGICAL MEMOIRS. 



On some Jurassic Cephalopoda /rom Wurtemberg. 

 By Dr. Albert Oppel. 



[Wiirttembergische Naturw. Jahreshefte, 1856, pp. 104-108.] 



1. Acanthoteuthis antiquus. — During his late visit to England, the 

 author obtained at Christian Malford* in Wiltshire, a very perfect spe- 

 cimen oi Acanthoteuthis antiquus\, with which he has since carefully 

 compared some conical bodies, similar to the alveoli of Belemnites, 

 that he has obtained from the clays with Am. Jason and Am. ornatus 

 from Gammelshausen, near Boll ; and from the result, he feels as- 

 sured that the correctness of dividing Belemnites Puzosianus from 

 Acanthoteuthis is well established, although the inside of the phrag- 

 macone of the latter has an organization but little differing from that 

 of the alveolus of a Belemnite. 



The phragmacones from Gammelshausen have a silicified inner cone, 

 which tapers at an angle of 25°, possesses a siphuncle and sheath, and 

 is covered vrith a thin calcareous layer. The latter appears to have a 

 similar structure to that of the Belemnite sheath ; its cross-fracture 

 shows a dark crystalline mass. In the English specimens it consists 

 of a white friable substance. The external form, on the contrary, in 

 specimens from both localities is closely similar ; and is quite different 

 from the sheath of the Belemnites. 



The author points out the importance of the presence of the si- 

 phuncle and the parallel sheath- walls in the specimens from Gam- 

 melshausen ; these not having yet been distinguished in the Christian 

 Malford specimens. In England the Belemnites Puzosianus fre- 

 quently occurs in the same clay with the Acanthoteuthis antiquus ; 

 which circumstance, in the author's opinion, has led to the associa- 

 tion of the parts of the two animals by some authors. In Wurtem- 

 berg, however, the Acanthoteuthis antiquus alone is found ; and this 

 affords an indirect proof of the distinctness of the two forms. 



2. Ammonites planorbis with Aptychus. — When in England last 

 year, the author saw in Mr. C. Moore's collection a fine suite of 

 Ammonites, particularly the Falciferi of the Upper Lias, enclosing 

 Aptychi^ Dr. Oppel also observed in the same collection an " undi- 

 vided'* AptychusX in an Am. planorbis, Sow. {Am. psilonotuSy 

 Quenst.). On his return home he determined to examine the Psilo- 

 noti of Wurtemberg, and the first specimen he split open exhibited an 

 " undivided" or univalve Aptychus lying in the body-chamber of the 

 Ammonite, much as in the known species, but evidently not divided 

 by a median fissure. As the Am. planorbis is the first Ammonite 

 occurring above the " bone-bed," it is the oldest Jurassic species. 



[T. R. J.] 



* The grey laminated clay with Acanthoteuthis belongs to the base of the Ox- 

 ford Clay ; and there are a considerable number of fossils common to it and the 

 ** Ornatus-clays " of the Continent. 



t Morris's Catalogue Brit. Foss., 1854, p. 289. 



X See also Mr. Strickland's paper on a univalve Aptychus in an Ammonite from 

 the lower lias, Quart. Journ. Geol. Soc. vol. i. p. 234. — Ed. 



