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PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



[Jan. 23, 



only be rendered possible by the discovery of more perfect specimens, 

 and perhaps of other parts of the animal." (p. 74.) 



Dr. Roemer then remarks on the evidence thus furnished of the 

 occurrence of naked Cephalopoda at an earlier period than had 

 hitherto been supposed ; and, in a note, he refers to Dr. Kner's paper 

 on Cephalaspis Lloyclii and C. Leivisii, disputing the conclusion at 

 which Kner had arrived, that these fossils are remains of Naked 

 Cephalopods, and affirming " that the structure of the shell of these 

 disks is rather that of Crustacea, and that their whole external form 

 leads to the supposition that they are allied to such palaeozoic Crus- 

 tacea as Dithyrocaris or PterygotusP Carefully executed figures 

 accompany the memoir from which these citations are made. 



In Leonhard and Bronn's ' Jahrbuch' for 1858, p. 55, Prof. Roemer 

 returns to this subject, in a short " Notice of a second specimen of 

 Arch&oteuthis* Dunensis, from the clay-slates of Wassenach, on the 

 Laacher-See," in which specimen the internal structure of the shell 

 is preserved. 



" The form and size of this specimen," says Prof. Roemer, " agree 

 essentially with those of the first specimen. Like the latter, it is 

 imperfect, the lower end being absent. The fossil is a coal-black, 

 brittle, horny substance, sharply defined against the slaty grey of 

 the matrix ; the thickness of the layer which it forms is about |rds of 

 a line, as can be distinctly seen by the transversely fractured circum- 

 ference. The sculpture of the surface is to be observed only over a 

 small space. Here it exhibits the same fine lines as the Daun spe- 

 cimen. For by far the greater part of its extent, the superficial 

 layer of the shell is destroyed, and the internal structure is revealed 

 so distinctly as to make this specimen particularly remarkable. It 

 consists of small prismatic cells, disposed perpendicularly to the sur- 

 face of the shell. The transverse section of the cells is irregularly 

 hexagonal, or even polygonal ; the diameter of the cells is such, that 

 three or four occur in the space of a line, whence the separate cells are 

 perfectly recognizable with the naked eye. The depth of the cells 

 is equal to about one-third of the thickness of the shell. The lower- 

 most layer of the shell appears not to take part in this coarsely 

 cellular structure, but to be much more compact. 



" If this structure be compared with that of the shell of Sepia 

 officinalis, L., the close analogy of the two is obvious. Only, in the 

 living genus the cells are much finer and are disposed in numerous 

 thin layers one over the other, whilst in the fossil species but a 

 single such layer is discernible. In any case, this cellular structure 

 of the fossil shell indicates its affinity rather with Sepia than with 

 Loligo, as I had previously supposed." 



The specimen from Wassenach thus described has now passed into 

 the collection of the British Museum ; and my friend Mr. "Woodward 

 (who had already divined the precise nature of the so-called Palmo- 

 teuihis in a note to p. 417 of his ' Manual of the Mollusca ') having 



* In Bronn and Roemer' s ' Lethsea Geognostica,' vol. i. p. 520, the name 

 Pal<eotei(this, having already heen employed by D'Orbigny, is given up, and 

 ArcJueoteuthis substituted for it. 



