568 VROT. T. "W. BBIDGE ON THE 



hooked process. In the eleventh and succeeding elements the 

 distal segments retain only a loose ligamentous connexion with 

 the postero-superior processes of their proximal segments, and 

 become entirely supported by the proximal segments of the next 

 succeeding radial elements, instead of by two contiguous segments 

 as is the case with the more anterior ones. 



There are fourteen spinose fin-rays w^hich gradually decrease 

 in length from before backwards, the hinder ones being purely 

 vestigial. The transversely elongated basal condyle of the first 

 spine fits into a similarly disposed groove on the distal end of the 

 proximal segment of the first radial element; the second spine 

 has the usual "chain-link" articulation with the distal segment; 

 and the remaining spines, as far as that normally belonging to 

 the ninth element, have similar articulations. The succeeding 

 spines have, however, simple cleft basal extremities, which clip 

 the distal ends of the proximal radial segments immediately 

 posterior to those to which they strictly belong. The last radial 

 element has no proper spine, although it supports the spine 

 belonging to the element immediately anterior. 



Median Dorsal Jin. — There are eleven radial elements, support- 

 ing a similar number of fin-rays, of which the first only is 

 spinose. All the elements are bisegmental. The first has a 

 hooked distal segment for articulation with the single spine; all 

 the others have simple cubical distal segments, the more anterior 

 of which have a " peg-and-socket " articulation with their fin- 

 rays, the posterior being simply embraced by the cleft bases of 

 the rays. Between the anterior and median divisions of the 

 dorsal fin there is a continuous series of fifteen vestigial proximal 

 segments in the form of slender splint-like ossicles, embedded in 

 the median fibrous septum between the dorsal muscles, and 

 indicating the primitive continuity of the two fins. 



The Finlets. — Six radial elements support the six detached 

 finlets, and form a continuous series with one another and with 

 those of the median dorsal fin. Their adaptation for mutual 

 support is brought about by the excessive elongation of their 

 postero-superior processes, which enables each process slightly 

 to overlap the base of the corresponding process of the next 

 succeeding proximal segment. Each of the elements is biseg- 

 mental, and its distal segment is clipped in the usual fashion by 

 the cleft base of the single multiarticulate and branched fiu-ray 

 of which each finiet is composed. 



