456 PEOP. ST. GEORGE MIVAET ON THE 



Second Dohsal Fin (Plate LXXIX. fig. 2). 



The skeleton of the second dorsal Jin is of the simplest possible character, consisting, 

 as it does, of a longitudinal series of subvertically placed, not quite contiguous, carti- 

 laginous radial pieces, forty-one in number. They increase very slowly in length post- 

 axiad from the first to about the eighth, remain much the same to the tenth, then rapidly 

 decrease in length to the fifteenth, then very slowly to the end. This skeleton is nowhere 

 in contact with the axial skeleton, but is separated from it by a wide tract of fibrous 

 tissue, which shows very plainly the lines of attachment of the intermuscular septa 

 sloping dorsad and preaxiad. The number of these does not at all correspond with 

 that of the fin-radials. 



The Ventral Fin (Plate LXXIX. fig. 4). 



The cartilaginous skeleton of this fin is very unlike that of other Elasmobranchs' ven- 

 trals, and recalls to mind the skeleton of their pectoral fins. Thus, e. g., if in the skeleton 

 of the pectoral fin oiAcanthias blainvillii the protruding preaxiad radials were shortened 

 and the basals fused and contracted, we should have very nearly the condition we find 

 in the ventral of Callorhynchus. We have, indeed, already in Scymnus lichia an example 

 of a single cartilage taking the place of the pro-, meso-, and metapterygium. 



In the ventral of Callorhynchus we have one large basal cartilage, the proximal 

 margin of which exhibits an articular concavity to fit on to the articular surface 

 (Plate LXXIX. fig. 5 a) of the pelvic cartilage. 



This basal cartilage must answer to the pro-, meso-, and metapterygium of anElasmo- 

 branch pectoral, and is deepest on the postaxial or metapterygial side. Its distal curved 

 margin is even and continuous, except a preaxial continuity with the radials, like that 

 found in Chhncera^. Here, however, the process is less distinctly marked. These radials, 

 at first very short, increase in length postaxiad to about the eleventh, and decrease from 

 about the fourteenth. At the apex of each is a small cartilaginous segment, longest in 

 the more preaxial radials, i. e. postaxiad of the second radial. The first radial bears 

 two small cartilages, side by side, at its distal end. The bases of the twelfth, thir- 

 teenth, fourteenth, and fifteenth radials have combined to form a small plate interposed 

 between their distinct proximal ends and the distal margin of the basal cartilage. 



The skeleton of the fin projects distad most a little protaxial to its antero-posterior 

 middle, about opposite the bottom of the concavity of the distal margin of the fin 

 as formed by its fin-rays. 



The Pelvis (Plate LXXIX. fig. 5). 

 The pelvic cartilage is very remarkable, and far more like the pelvis of a Batrachian 

 than is any other fish-pelvis known to me. The right and left halves are separate. 

 Each consists of a solid mass of cartilage (/p), which may be called ischio-pubic, from 



Gegenbaur's ' Daa Skelet der Gliedmassen der "Wirbelthiere im Allgemeinen,' plate xvi. fig. 22, E. 



