rijsrs OP GATsroiDS and teleosts. 535 



As a rule each element is of the same thickness throughout its 

 length, or nearly so, and the proximal segments are never dagger- 

 shaped. Concrescence is still evident in the fusion of the 

 proximal segments of the first and second, the eleventh, twelfth, 

 and thirteenth, and those of the fourteenth, fifteenth, and 

 sixteenth, into a single basal segment in each case. The radial 

 elements are but feebly ossified. The first, including the basal 

 segment which it shares with the second, the last two, and the 

 distal segments of all, are wholly cartilaginous, but, with these 

 exceptions, the proximal and mesial segments are partially 

 ossified. In all cases, however, ossification extends only to the 

 formation of a thin crust of superficial bone round an axial core 

 of unaltered cartilage, and leaves the extremities of the segments 

 entirely free from ossific deposit. There is no definite method of 

 articulation between the segments of contiguous elements, 

 although, as in the Elasmobranchs, the latter afford one another 

 mutual support by their parallel disposition, fairly close appo- 

 sition, and fibrous connexion throughout the greater part of 

 their length. 



The characteristic horny fibres of the Elasmobranchs and 

 Holocephala are here replaced by partially ossified, multiarticu- 

 late dermal rays, which, as in the higher Granoids and in Teleosts, 

 are bifurcate proximally and branched distally. The dermal 

 rays still, however, retain traces of the characteristic arrangement 

 of the horny fibres of the preceding groups, in the fact that their 

 cleft proximal extremities embrace not only the distal but to 

 some extent also the mesial segments of their supporting radial 

 elements ; and also in their greater number. Altogether there 

 are about forty dermal rays, or approximately about two and a 

 half as many as the radial elements which support them. 



Anal fin. — This fin is very similar to the dorsal. There are, 

 however, only ten radial elements, all of which are trisegmental. 

 The second is slightly the longest of the series, those behind 

 gradually decreasing in length from before backwards. The 

 proximal segments of the first and second, and those of the third 

 and fourth, coalesce to form a single basal segment in each case. 

 As far as the particular segments which undergo partial ossification 

 are concerned, the anal difi'ers but little from the dorsal fin, but 

 ossification is somewhat more complete, and to a greater extent 

 replaces the primitive cartilage in the former than in the latter. 



About twenty-five dermal rays are supported by the radial 

 elements. 



