BY WILLIAM A. HASWELL, M.A., B.SC. 87 



between that of Carcharias and that of Oallorhyaclms * — the basal 

 elements in the latter being reduced to two, of which the posterior 

 may be regarded as the homologue of a coalescent meso- and 

 nietapter ygiu m . 



The whole of the long pointed fin of Carcharodon is supported 

 by a framework of cartilaginous rays which extend nearly to its 

 apex and are closely united into a continuous triangular plate. The 

 middle rays, i.e., those which reach nearly or quite to the apex of 

 the skeleton of the fin, broaden out considerably distally, and 

 sometimes divide. Between the distal portion of adjacent rays in 

 the front half of the apical part of the fin are intercalated a 

 series of accessory rays, an arrangement which I have not met 

 with in any other form, though a rudiment of it is traceable 

 in Meter odontus Phillipi. 



The Pelvic Fins. 

 The pelvic cartilage presents a large oval aperture in its outer 

 half near the anterior border ; its outer extremity is produced into 

 a process with which no fewer than six rays articulate. The basai 

 cartilage is strong and curved, convex above, flat below ; at its 

 distal extremity are two small cartilages with which the long 

 tapering flexible cartilage of the clasper articulates. The last ray, 

 which is very short, is attached exclusively to the base of the 

 cartilage of the clasper. 



The Dorsal fins. (Plate I., fig. 4.) 

 The dorsal fin is supported by a cartilaginous skeleton which 

 is separated by a fibrous interval from the spinal column. It 

 consists of about twenty-eight rays, which slope for the most part 

 backwards and upwards. The first ray is very short, but presents 

 traces of division into three segments. The second, which is a 

 little longer, divides into two branches ; the third is simple, and 

 consists of three segments, of which the basal is ranch the longest ; 

 the fourth is bifurcated, and each of the branches presents two 

 articulations. The next six rays are either distinctly bifurcated near 



* Vide Mivart, 1. c. 



