448 PROF. ST. GEORGE MIVART ON THE 



apices of the two most pieaxial distal cartilages are pointed ; but the rest are truncated 

 apically. 



The Ve-\tkal Fin (Plate LXXVI. fig. 5). 



Here we have a very simple skeleton, consisting of sixteen radials, whereof two are 

 attached to the pelvic cartilage (p), and the rest to an antero-posterior basal cartilage (b) 

 of nearly equal width throughout. The fourth radial is the longest ; and thence they 

 decrease gradually in length in each direction. 



Distal cartilages are attached, one to the apex of each elongated cartilage, from the 

 second to the eighth inclusive. That attached to the fourth long cartilage is the 

 longest ; and thence they rapidly diminish, both preaxiad and postaxiad. 



The Pectoral Fin (Plate LXXVI. fig. 4). 



In this fin there are but two basal cartilages (m and ^), separated by a wide mem- 

 branous interval. They are both long cartilages, and of subequal length. 



The metapterygium is undoubtedly represented by the more postaxial of these two 

 cartilages ; it supports distaUy six radials. 



The mesopterygium may possibly be represented, as well as the propterygium, by the 

 more preaxial basal cartilage ; but I am inclined to regard it as absent, since (as before 

 said) it is hard to find any definition of a " mesopterygium " save that of " a basal carti- 

 lage occupying the middle region of a limb-axis." This absence is, moreover, the less 

 surprising when we consider the conditions which exist in Chimmra and Callorhynchus. 



The iiropterygiiim is represented by the preaxial basal cartilage, which is as elon- 

 gated and large as the mesopterygium. It has a strongly concave mediad margin, and 

 expands distally to give attachment to nine radials. The most preaxiad radial creeps 

 up, as it were, along the preaxial margin of the propterygium to about its middle, thus 

 presenting a much less development of what we found in Ginglymostoma. It consists 

 of three segments. In the radials attached to the propterygium the middle segment is 

 the broadest, and the distal segments are so applied to their supporting cartilages that 

 the adjacent sides of the distal ends of these (from the fourth to the ninth) support a 

 distal cartilage between them. 



One radial has its proximal apex placed, not against, but between the pro- and 

 metapterygiun. Its distal cartilage is medianly divided, so that there are two little 

 terminal cartilages placed side by side. The same is the case in the terminations of the 

 three next more postaxial rays. The last three (most postaxial) rays do not show any 

 distinct signs of segmentation in my specimen. 



It is the proximal part of the limb-skeleton which projects furthest distad. 



