246 
J. STUART THOMSOX. 
Each of the rays, with the exception of the first, contains 
two horn}' fibres which are separated from one another b}' 
connective tissue, and approach one another near the base. 
Each ray has an anterior and posterior basal enlargement. 
From the anterior of those a muscle passes almost vertically 
in a ventral direction and attaches itself to the lower part of 
the ray-carrier. This muscle acts as au erector elevating 
the ray. On the other hand, from the posterior process, a 
muscle passes obliquely downwards along the neck of the 
ray-carrier and fixes itself slightly dorsal to the attachment 
of the anterior muscle. This muscle acts as a depressor, 
lowering the processes into the groove. 
The form of the first anterior process differs slightly from 
those just described. It contains only a single horny fibre, 
which divides at the base, and there are three sinall, basal 
processes to which the tendons of muscles are attached. It 
also differs from the smaller processes in that the ray is more 
directly connected with the ray-carrier by means of embryonal 
cartilage. 
Transverse sections through the rays near their apexes 
show au external, many-layered epithelium containing mucous 
glands; within this a deeply pigmented layer is situated, 
which surrounds a mass of centrally disposed connective 
tissue. The latter contains blood-vessels and two horny 
fibres. 
The individual rays are, as previously stated, connected 
with one another by a fold of skin near the base. 
The vibratile fin is supported in its position by means of a 
ligament, which surrounds and covers the spinous processes 
of the vertebrae, and dorsally to these also envelopes the 
centrally situated ray-carriers. This paiied ligament takes 
its origin in the supra-occipital, and it proceeds in a posterior 
direction on either side of the ray-carriers, but on arriving 
at the aboral fin the two layers, right and left, unite into 
one. 
The fin is, as previously stated, situated in a groove, whose 
internal boundaries are chiefly formed by the very prominent 
