of Edinburgh, Session 1879-80. 
457 
4. The Structure of the Comb-like Branchial Appendages and 
the Teeth of the Basking Shark (Selache maxima). By 
Professor Turner, M.B., F.R.S. 
Attention was drawn to the statements made on the position of 
peculiar comb-like fringes on the branchiae of the basking shark by 
Gunnerus, Pennant, Low, Mitchell, Foulis, Brito Capello, Cornish, 
Steenstrup, Pavesi, P. & H. Gervais, Percival Wright, and Allman, 
and to the structure of these fringes by Hannover and MM. 
Gervais. The author then proceeded to give a detailed description 
of the structure of the plates forming these fringes from a specimen 
presented to him by the Rev. M. Harvey of St. John’s, Newfound- 
land, the general summary of which is as follows : the whole peri- 
phery of a plate consisted of a hard unvascular dentine, the tubes in 
which were very distinctive ; in a considerable part of the shaft 
these tubes arose from a single central pulp cavity, hut in the semi- 
lunar attached base of the plate the single central cavity did not 
exist, but was replaced by a set of anastomosing vascular canals, 
which collectively represented a pulp cavity, and which gave origin 
to numerous characteristic dentine tubes. It was suggested that these 
plates were developed in the mucous membrane covering the branchiae 
after the manner of teeth. Although these plates act, like whale- 
hone plates, to separate from the water the small organisms on which 
this shark lives, they were shown to be essentially different in struc- 
ture and mode of origin, the matrix of whalebone being a cornifica- 
tion of the ephithelium of the palate derived from the epiblast, whilst 
the matrix in the shark’s branchial plates is a calcification of dermal 
or sub-epithelial structure, and therefore derived from the mesoblast. 
Reference was made to the observations of Andrew Smith on 
Rhinodon, in which an apparatus having a similar office, but probably 
a different structure, was seen in that shark ; and to the observations 
of Van Beneden on a comb-like fringe found fossilised in the Antwerp 
Crag. 
The structure of the small conical teeth of the basking shark was 
then described from a specimen also presented by the Rev. M. 
Harvey. They were shown to have an external layer of hard un- 
vascular dentine, covering an extensive core in which relatively large 
