FINS OP GANOIUS AND TELEOSTS. 595 



is to be found in front of tlie first. Thus in the latter position 

 there may be only one vestigial element (e. g. Perca), or three 

 (Mesoprioji, Pagellus, Caranx), or seven (Githarinus) or eight 

 (Abramis) ; and in a few instances the number may be so con- 

 siderable as to extend the series to the posterior face of the skull, 

 as, for example, where the numbers are seventeen (Cor eg onus), 

 or eighteen (Glupea). In some instances such vestigial elements 

 are interposed between the ray-bearing elements of fins which 

 externally are discontinuous : thus, between the mesial and 

 posterior dorsal fins of Gadus (sglefinus there are three vestigial 

 elements; between the anterior and posterior dorsal fins of 

 Scomher scomber fifteen ; and in a similar position in Mugil 

 capita three. The presence of these ossicles must be regarded 

 as indicating the existence of a primitively more extensive dorsal 

 fin ; and in the case of Scomber, Gadus, and Mugil proves also the 

 original continuity of fins which in the adult are distinct. No 

 vestigial elements are ever present anterior to the first ray-bearing 

 element of the anal fin, although somewhat rarely there may be 

 one behind the last. 



Eadial elements are in ligamentous connexion with one 

 another ; and in the absence of definite articulations, inter se, this 

 may be the only bond of union between them (e. g. Cucloptei-us). 

 Where the elements are trisegmental, a ligament (interof*sicular 

 ligament) extends backwards from each distal segment to the 

 mesial and distal segments of the next succeeding element. In 

 the absence of a mesial segment, the postero-superior or postero- 

 inferior process takes its place as a point of attachment for the 

 ligament; and when both mesial and distal segments are wanting, 

 the ligament extends between the distal extremities of successive 

 proximal segments. In some genera the ossification of the 

 ligaments, or of portions of them, may give rise to bony hook- 

 like processes for articulation with the dermal fin-rays (Solocen- 

 trum, Mugil, Anarrhichas). 



Selations of the various Segments of the Radial Elements to the 

 Dermal Fin-rays in different Teleosts. 



As in Lepidosteus and Amia, so in the majority of Teleosts, each 

 element normally possesses only a single fin-ray ; but owing to the 

 fact that the distal segments which directly support the fin-rays 

 articulate not only with the mesial or, in their absence, the 

 proximal segment of the same radial element, but also with the 

 proximal segment of the next succeeding element, it is very 



47* 



