JINS OF GANOIDS AND TELEOSTS. 531 



of ovoidal nodules of cartilage in connexion with the distal 

 extremities of the interspinous bones of the mesial fins o£ this 

 fish, remarks (p. 24) :— " I have not met with cartilages of this 

 kind in any fish which has come under my notice, and I can find 

 no account of any such in works at my disposal. I regard them 

 as representing a second or distal series of radials or pterygo- 

 phores, the interspinous bones forming the proximal series." 

 That Parker was correct in his view of the nature of these 

 cartilages there can be no doubt ; and so far as I have been able 

 to discover he appears to have been the first to recognize the 

 existence of bisegmental '•' interspinous " elements in any Teleost. 

 More recently it has been shown by Eyder [2j and Harrison [3], 

 that in the development of the fins in those Teleosts which they 

 examined each " interspinous " element consists of a proximal 

 division to which is appended a distal nodule of cartilage for the 

 immediate support of a dermal fin-ray, and hence, as in Reqa- 

 lecus, such elements are bisegmental. It is, however, by no 

 means difficult to show that these cartilages, or their equivalents 

 in the form of osseous nodules, are very generally present in 

 Teleosts ; and further, that in not a few families the intercala- 

 tion of a hitherto unrecorded * series of mesial ossicles betw^een 

 the proximal and distal segments renders such "interspinous 

 elements " trisegmental. 



The main object of the present communication is to describe 

 (a) the degree of segmentation and the more characteristic 

 modifications of the " interspinous elements " of the dorsal 

 and anal fins of Teleosts ; (&) the extent to which such modifi- 

 cations are characteristic of particular groups or families ; 

 and (c) th^ various methods by which in different families the 

 segments of the " interspinous " elements contribute to the 

 support of the fin-rays. With these ideas in view a large 

 number of Teleosts were examined, and as far as possible the 

 species selected for examination are typical representatives of 

 the leading subdivisions of the group. Although this paper was 

 originally intended to deal exclusively with Teleosts, it has been 

 thought desirable to include the Ganoids, and also to refer 

 briefly to the Holocephala and Elasmobrauchs, in order that an 

 accurate comparison of the fin-supports in these four great 

 groups of Wishes might be made. 



The early stages in the development of the mesial fins of 

 * See reference to Giinther's figure of Beryx decadactyhis, p. 563. 



43* 



