﻿C0CC03TEIDJB. 289 



plate (d.) is tho closely arranged series of robust neural 

 arches with their spiues (?i.), 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 

 (h.), 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 (6 l , 6 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 Diplacanthug 

 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 (£>?*>.), 

 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- 

 ekeletal elements, being only calcified in a thin layer at 

 the surface. Portions of a longitudinal white streak (I. I.) 

 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 (x.) 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. 



44586. Cranial shield, with displaced maxillo-suborbitals, in coun- 

 terpart, shown of the natural size in PI. VII. fig. 1. The 

 specimen is apparently un crushed, 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 tuberculations are unusually coarse. 



Purchased, 1873. 



PART II. V 



