C0CC0STEID JJ. 
289 
plate ( d .) is the closely arranged series of robust neural 
arches with their spines (n.), bounding above the narrow 
vacant space (not.) originally occupied by the persistent 
notochord ; and some of these arches exhibit indications 
of a zygapophysial union. Below the notochordal space 
there is a corresponding series of haemal arches and spines 
(A), gradually becoming much lengthened towards the 
end of the abdominal region and shortening again in the 
caudal. A short distance behind the dorsal shield the 
neural spines also become lengthened for the support of 
the double series of about 13 basal cartilages (b 1 , b 2 ) of 
the dorsal fin, which are as robust as the neural spines 
themselves and are directly apposed to the ends of an 
equal number of the latter. The membrane of the dorsal 
fin is not observed, but remains of a small Diplacanthux 
occur in the position it would originally occupy. Behind 
and above the posterior ventro-lateral plates ( p.v.l .) are 
preserved the right and left pelvic basipterygia (plv.), 
attenuated above, but widened to a club-shaped extremity 
below, with one or two deep pits or foramina (/.) pene¬ 
trating this expansion. Apposed to the broad end of one 
of these cartilages is a series of four or five short stout 
rays (r.), while directly behind the same cartilage are 
indications apparently of longer rays of a similar character 
(see also No. P. 3215); these, like all the other endo- 
skeletal elements, being only calcified in a thin layer at 
the surface. Portions of a longitudinal white streak (l.l.) 
along the vacant space between the neural and haemal 
arches are suggestive of dermal calcifications along the 
lateral line (see also No. P. 3215) ; and the problematical 
azygous plate (a?.) at the commencement of the caudal 
region, already noted in several specimens, is especially 
conspicuous. This plate is quadrate in form, with a 
convex inferior border, is evidently very thin, and exhibits 
prominent concentric lines of growth. Purchased, 1872. 
44588 . Cranial shield, with displaced maxillo-suborbitals, in coun¬ 
terpart, shown of the natural size in PI. YII. fig. 1. The 
specimen is apparently uncrushed, thus exhibiting the 
original contour ; most of the sutures and some of the 
sensory canals are distinct, and are seen to be disposed as 
in Dr. Traquair’s restoration (fig. 42, p. 279); and the 
superficial tubereulations are unusually coarse. 
Purchased , 1873. 
PART II, 
V 
