104 _ Prof. H. A. Nicholson—On the Favositide. 
ing fin-rays or radials, of which there are three or four to each 
neural spine; they are more slender than the latter, but have the 
same granular structure. They gradually increase in length towards 
the posterior third of the body, whence they again fall away towards 
‘the end of the tail. The abdominal region extends for 13 inch behind 
the head: no ribs are visible, the termination of the abdomen being 
marked by the commencement of a series of hamal elements quite 
similar in configuration and structure to the neural ones above, and 
these now extend to the extremity of the tail. No fin-rays are 
seen on the ventral aspect of the skeleton, nor have I seen any trace 
of any dermal hard parts. 
This is indeed one of the strangest fishes as yet yielded by these 
Eskdale deposits, which have proved so rich in paleichthyological 
treasures. We are not aware of any ganoid, recent or fossil, whose 
body is entirely destitute of dermal hard parts, for even the all but 
naked Polyodon of the present day and also the Carboniferous 
Phanerosteon have still a few scales on some part of their surface. 
It seems also scarcely probable, that the apparent absence of mem- 
brane bones from the head and shoulder-girdle is entirely due to 
deficient preservation, and the granular structure of the vertebral 
apophyses and radials is not paralleled so far as I know in any 
Ganoid. It certainly is not an ordinary Ganoid, nor is it an Acan- 
thodian. On the other hand, its affinity to the Selachii seems to be 
indicated by the position of the shoulder-girdle, and by the granular 
calcification of the vertebral apophyses and radials, and probably 
also of the head and shoulder-girdle. If it be a Selachian, it is 
certainly one of a very primitive and at the same time aberrant type. 
In its long dorsal fin, it resembles Xenacanthus, but there is no 
cephalic spine, apparently no paired fins (though this may indeed 
be due to defective preservation), the vertebral centra are more 
developed, and the two rows of dorsal interspinous cartilages or 
“« Flossentriiger ” described by Kner in that genus seem to be absent. 
It is certainly a new, as well as a most interesting form, for which 
I accordingly propose the name of Chondrenchelys problematica. 
I1I.—On tur Derecrion or Murat Pores iy THIn SECTIONS OF 
THE FavosiTipm. 
By H. Atteyne Nicuouson, M.D., D.Se., F.G.S., 
Regius Professor of Natural History in the University of Aberdeen. 
Sa text for the following brief remarks on the recognition of 
mural pores in thin sections of the Favositoid Corals, I may 
quote a note appended by Mr. James Thomson, F.G.S., to a recent 
paper on the genus Lithostrotion (Trans. Edin. Geol. Soc. vol. v. 
part i. p. 881). The note in question is subjoined, the quotation 
being verbatim, and, I may add, literatim also :-— 
“We may, however, attach an undue importance to microscopic 
examinations. Need I refer to the point raised recently by that 
erratic and energetic worker, Prof. Alleyne Nicholson, regarding 
mural pores in the genus Alveolites, the type of which is also in Dr. 
