562 PEOP. T. W. BRIDGE ON THE MESIAL 



the mode of articulation of tlie first spine ; but I am inclined 

 to think that the chain-link in this case is due to a modification 

 similar to that by which the same kind of articulation is brought 

 about in the case of the distal segments and spines of the rest 

 of the fin, viz., by the ingrowth of the basal extremities of an 

 ordinary clef fc ray through the distal end of a proximal segment. 

 There is a striking contrast between the radial elements already 

 described and the fifteen (r.e."-r.<?.^') supporting the sixteen 

 soft rays of the hinder section of the dorsal fin. The elements 

 are all trisegmental, consisting of proximal (p.s.), mesial (m.s.), 

 and distal (d.s.) segments, which have almost precisely similar 

 relations to one another, and to those of contiguous elements, as 

 in the Cyprinidse and other Teleosts with trisegmental radial 

 elements. Behind the fifteenth there is a vestigial proximal 

 segment (v.e.) suturally united to the one in front. 



Each fin-ray is cleft basally and clips the distal segment of 

 its proper radial element, although, as usual, the ray is partly 

 supported by the next succeeding proximal segment. The 

 distal segment of the last element contributes to the support of 

 two rays. 



Immediately anterior to the first radial element of tbe dorsal 

 fin there are two vestigial elements without rays. 



Anal fin. — There are twelve radial elements (fig. 23) and 

 fifteen fin-rays, and, of the latter, four are spinose and the 

 remainder soft and multiarticulate. 



Tbe third to the twelfth radial elements inclusive {r.e.^-r.e}^^ 

 are trisegmental and in every respect similar to those in the 

 hinder section of the dorsal fin, but the first and second (r.e}- 

 r.e.^) have only proximal and distal segments {p.s.,d.s.). The 

 proximal segments of the first two elements are exceptionally 

 long and stout, and are firmly, but suturally, united together ; 

 the remainder are slender and gradually decrease in size as they 

 extend backwards. The distal segment of the third radial 

 element is a simple cubical ossicle similar to those of the 

 succeeding elements ; but those of the first and second consist 

 of a cubical body produced distally into anterior and posterior 

 hook-like processes, of which the anterior is simply due to the 

 ossification of the interossicular ligament in continuity with the 

 segment itself. Tbe proximal and distal segments of the first 

 two radial elements furnish either peg-and-socket or chain-link 

 articulations for the first four spinose fin-rays. A tubercle on 



