14 BULLETIN OF THE 
each other and united by ligament, except at the extreme end, where 
there is a small space in which the cartilages appear to have coalesced. 
They approach each other in an angle of about forty-five degrees. The 
scapula is less angular and more slender; at its upper end there is an 
elongate flexible segment. 
The metapterygium (mtp) of the pectoral. is about half as long as the 
fin itself; it is slender, broader backward, tapered in front and articu- 
lates by a small surface with the coracoid. It is in two segments, and 
bears two radials at the end and ten on the side. 
The mesopterygium (msp) is a large triangular plate extending upward 
in an angle between the propterygium and the radials, but not sepa- 
rating the metapterygium from the coracoid, as in the sketch; it articu- 
lates with the process in the articular surface of the coracoid and with 
the propterygium. 
The propterygium (prp) is small, subtriangular or oblong, and — 
articulating in the cavity of the articular surface of the coracoid — fur- 
nishes a convex facet for the mesopterygium. It is not fused with the 
coracoid, as might be understood from the figure. The articulation is 
similar to that of Heptabranchias, as figured by Mivart, Fins of Elasmo- 
branchs, Pl. LXXYV. fig. 3. 
The radials are in three series, of which those of the outer are small 
and short, and those of the inner elongate. Of the latter, three or four 
of the anterior have coalesced in an irregular plate. 
The Cartilages of the Pelvis and Ventrals. 
Plate XI. Fig. 1, Plate XII. 
The pelvis is a broad comparatively thin plate of cartilage about twice 
as long as wide. On the upper surface it is concave, and has a ridge 
along each side. Below it is convex and has a median ridge which bifur- 
cates forward. Toward the vent the border is concave; in front the 
margin is convex. The anterior twelve radials articulate directly with 
the side of the pelvis. Several of the foremost of these rays are only 
partly distinct from each other. 
The peculiar shape of this pelvis suggests an embryonic character of 
other sharks. In embryos the pelvis is longer than in the adult, in 
comparison with the transverse measurement. An embryo of Hepta- 
branchias before me has it half as long as wide, proportions which 
are intermediate between those of the adult and an adult Chlamy- 
doselachus. 
