418 ON PTERASPIS DUNENSIS 
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 Lloydii and C. Lewisti, 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 palozoic 
Crustacea as Dithyrocaris or Pterygotus.’ Carefully executed figures 
accompany the memoir from which these citations are made. 
In Leonhard and Bronn’s ‘Jahrbuch’ for 1858, p. 55, Professor 
Roemer returns to this subject, in a short “ Notice of a second speci- 
men of Archeoteuthis! 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 Professor 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 2rds 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 
specimen. 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 
surface 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 
lowermost layer of the shell appears not to take part in this coarsely 
cellular structure, but to be much more compact. 
“Tf this structure be compared with that of the shell of Sepza 
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 
1 In Bronn and Roemer’s ‘ Lethzea Geognostica,’ vol. i. p. 520, the name Paleoteuthis, 
having already been employed by D’Orbigny, is given up, and Archeoteuwthis substituted 
for it. 
