430 



Fig. 2. Dissection of accessory fins 

 of specimen No. 1 showing the various 

 cartilages. For A, B and C references, 

 see text. 



any — is somewhat doubtful. The basal piece is roughly hour-glass- 

 shaped, with a thick waist, and laterally compressed. The second is 

 the largest, is almost triangular and to it the two fins are attached. 

 The other three pieces are flattened plates narrower than the others. 

 All the five are joined end to end in a series, forming a curved 



angular rod (Fig. 2 a). The larger 

 of the two fins is attached as 

 shown in Fig. 2 to the "girdle" 

 at the apex of the triangular 

 portion. There is no freedom of 

 movement at the junction. The 

 fin is spoon-shaped, the concavity 

 being directed downwards. It is 

 made up of a number of radials 

 of different form and size. Along 

 the margins they are slender and 

 of the usual rod-like form; the 

 inner region consists for the most 

 part polygonal pieces (Fig. 2 b). 

 The other fin, the smaller of the 

 two, possesses quite a different 

 structure. Here there is a basale of six elements carrying radials of 

 normal form upon the postaxial border along the whole length. There 

 is a single radial upon the preaxial side, arising from the distal basal 

 element (Fig. 2 &). 



With regard to specimen No. 2 I am unable to give anatomical 

 details owing to the fact that only the preserved skin is available for 

 examination. The other parts had been destroyed before I secured 

 the specimen. The skin has been excellently preserved and shows 

 well the character of the accessory part. It is simpler than the 

 previous one, consisting of one portion only. It is placed in the mid- 

 dorsal line 10,5 inches fron the snout ano 7,5 inches from the base 

 of the tail, and has a base of 1,75 inches or thereby. Its position 

 is behind the scapula and clear of it; it ascends vertically for a height 

 of about two inches and then bends over to the right side, the remainder 

 forming a large domed fan-like structure having the concavity 

 directed downwards. Along the anterior edge it measures 3,75 inches. 

 It appears to have been attached to the neural ridge; it contains 

 radials of the usual form and apart from the convexity has a close 

 resemblance to a pectoral fin. It appears, in fact, clearly a fin of 

 this order. Whether basalia were present cannot, from the condition 



