flNS OF ELASMOBRAHCHS. 



451 



SPINAx NIGEK. 



Dorsal Fin (Plate LXXVII. fig. 4). 



The dorsal fin of this Shark presents a great similarity to that of AcantJiias hlainvillii ; 

 only coalescence has here been carried still further. 



One hasal cartilage, besides the spine, represents by itself the two of Acanthias, and 

 forms a longer and narrower triangular plate than in the last-mentioned genus. 



The median cartilages are but two in number, besides the elongated piece applied to 

 the postaxial side of the spine. This piece is longer than in Acanthias. The median 

 cartilage postaxial to it (or second median cartilage) is much as in Acanthias, save that 

 it rises to form the distal margin of the most preaxial part of the fin-skeleton behind 

 the elongated piece just mentioned. 



The third, or most postaxial median cartilage (m 3), is greatly enlarged antero- 

 posteriorly, compared with that of Acanthias blainvillii, and seems to answer to the 

 two postaxiad median cartilages of that species fused together. 



The distal cartilages of Acanthias blainvillii are here represented by a narrow elon- 

 gated cartilage, which shows an obscure and doubtful segmentation into three parts. 

 As in Acanthias blainvillii, so here, the cartilaginous skeleton of the dorsal fin is 

 applied to the axial skeleton by the proximal end of the spine and the most preaxial 

 part of the base of the large cartilage which is placed just behind the spine. More 

 postaxially this skeleton is connected with the axial skeleton by fibrous membrane only. 



Fig. 1. 



SCYMNUS LICHIA. 



Pectoral Fin. 



This species is very interesting i, because it seiTes to 

 show how one single cartilage may represent the pro-, 

 meso; and metapterygium — all three. For there is but 

 one basal cartilage, which supports all the radials (some 

 seventeen in number), and is in the form of a large sub- 

 triangular plate, with its truncated apex proximad. The 

 postaxial border is the longest ; and its distal margin slopes 

 obliquely postaxiad and ventrad. 



' Eepresented in Gegenbaijr's ' Untersuchungen,' plate ix. fig. 9. 



Eight pectoral fin of Scymnus liehia. 



