442 PROF. ST. GEORGE MIVAET ON THE 



The more preaxial dorsal cartilages are two in number to each vertebra. The most 

 postaxial ones are, like the haemal cartilages, one to each vertebra ; and in the inter- 

 mediate space they pass gradually from one condition to the other. 



Both the dorsal and ventral cartilages are single and unsegmented, save as above 

 mentioned, and there is neither bifurcation nor coalescence. 



The dorsal cartilages are not only much more numerous but also much inferior in 

 size to the ventral cartilages. 



The Ventral Fin (Plate LXXIV. fig. 5). 



This fin is supported by a series of elongated closely set cartilages, to the greater 

 number of which a second (distal) cartilage is appended, there being thus a distal series 

 of smaller cartilages. Proximally, all the rays but the first unite with a continuous 

 thick bar of cartilage, which runs more or less antero-posteriorly and at right angles 

 to the elongated cartilages which join it. 



The first ray, which is stouter than the others, does not join this bar, but is united 

 with the pelvic girdle (p). 



The number of elongated cartilages is twenty ; and there are seventeen distal car- 

 tilages attached respectively one to each of the elongated cartilages, except the three 

 most postaxiad. The first seven or eight distal cartilages are of subequal length ; they 

 then rapidly shorten postaxiad. 



If we compare this fin-skeleton with that of the dorsal fin, the resemblance between 

 its elongated and distal cartilages and the median and distal cartilages of the dorsal is 

 striking. May, then, this antero-posteriorly elongated bar answer to the basal cartilages 

 of the dorsal fin coalesced together "? This elongated cartilage has not a slight resemblance 

 to the metapterygium of the pectoral fin ; and the large preaxial radial may be com- 

 pared with the propterygium. 



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



The pectoral limb is supported by a cartilaginous skeleton, consisting, as usual in 

 Elasmobranchs, of a pro-, meso-, and metapterygium, with appended segmented rays. 



The metajiterygium (c) is the largest of the three, club-shaped, and narrowing proximad. 



The mesopterygium {h) is less than half the size of the metapterygium, and acutely 

 subtriangular in shape, with the apex proximad. 



The propter ygium{a) is a little smaller and also acutely subtriangular, but with the apex 

 distad. To it is appended the most preaxial ray (or radial), which is rather wider than 

 the succeeding ones, and is twice segmented, the terminal segment ending distally in a 

 sharp point. The broad distal end of the mesopterygium supports the three next radials, 

 each of which also consists of three segments. The terminal segment of the first of these 

 three rays is also pointed distally ; but that of each of the two succeeding rays is obliquely 

 truncated. All the other rays, or radials, are attached to the metapterygium, radi- 



