eae ON THE SCAPUnA (?), CoRACOTD, 
been more nearly square than either of the other two forms, and 
is characterized by a very narrow border, which shows only one 
. Th 
bony network of the central area is fine and indistinct, with a 
longitudinal peieoniiern of the meshes, as in the second species; 
the punctures are numerous, rather large, and longitudinally 
oval. 
vi 
“The last i is apparently of a mere cast of the under 
surface ; but a small portion of the scale, exhibiting the upper 
surface, is sdhcrent, and proves that it is minutely striated in an 
irre en manner — strie for the most part having a 
“The peculiar tectannndiar form distinguishes these from all 
the cycloid scales with which we are acquainted; and they are 
uch thi 
cca ted on the surface, aa usually “atthe concentric lines 
of growth over the whole surface ; it is also generally found split 
open, exposing to view the int ternal structure, when the con- 
seen with the internal structure thus exposed: at least we have 
never seen the concentric lines of growth and radiating strie pass 
beyond the eigen the. under surface being usually exposed to 
view. This is shown in our second species, the specimen 
being one on one slab i in relief, the cast of the under-side 
in intaglio on the other 
wh 
other parts are comparatively ¢ common, x nting, then, that Mr. 
Atthey’s discoveries are correctly diagnosed, for t T have never had 
the opportunity given me of even seeing these imens re 
can be no hesitation in affirming their close similarity in form to 
the scales of Ceratodus. Reasoning from analogy would certainly 
lead one to infer that Ctenodus had scales 
The forms of pions: fins and tail are xin unknown to me, but 
Mr. Atthey, from poor rae crushed specimen of ©. elegans he 
possesses, and to which I referred in speaking of the scales, 
