478 
WELLBURN : ON THE GENUS CCELACANTHUS. 
The Lateral Line is very rarely seen. It probably runs (as 
shown by Eeis"^) from a point near the junction of the clavicle with 
the supra-clavicular bone to a point well back on the body prolonga- 
tion of the caudal fin. 
Pectoral Arch.— The membrane bones of the shoulder girdle 
are, although slender, always conspicuous, and seem to have been 
covered by the skin. There are a pair of long, slender, gently curved 
clavicles (CI.), which exhibit a robust post-clavicular process (P.Cl.Pr.). 
They articulate above with a small supra-clavicle (S.Cl.), while a 
long, slender infra-clavicle (LCI.) overlaps its lower spatulate extremity. 
The latter element curves sharply forwards and inwards, termi- 
nating in a triangular expansion where it meets its fellow of the 
opposite side in a median suture. 
Fins. 
The paired fins are well developed and obtusely lobate. 
Pectoral Fin. — A specimen in the writer's collection shows 
that the internal skeleton of the lobe of this fin consists of several 
superficially ossified basal supports (Ba.S.), which are jointed at 
their proximal extremities to the post-clavicular process (P.Cl.Pr.), 
whilst distally each is opposed to the proximal ends of one or more 
of the dermal rays (D.R.) of the supports. The anterior four are 
elongated and more or less uniform in thickness. The fifth is more 
hourglass-shaped, while the sixth is more robust and widely ex- 
panded distally. The dermal rays of the fin increase in length from 
the anterior border to the middle of the lobe, whence they decrease 
backwards, and finally become extremely fine. AW the rays are 
slender and closely articulated distally. 
Pelvic Fins. — These fins are supported by a pair of basipterygia 
(Ax. 4), having the following characters, viz., distally, where 
they would join the basal supports, they are broad and expanded, 
the proximal half form a thin, more or less triangular expansion, 
the expansion being strengthened by three thickenings, one being 
central and two lateral, while springing from the centre of the bone 
are two inwardly directed precesses which are loosely apposed in 
* Op. cit. 
