niS'S OF GAKOIDS A'NVl TELEOSTS. 537 



that is at or near the junctions of the proximal and mesial seg- 

 ments, and distally are the elements in actual contact or fairly 

 close relations with one another. Concrescence is less marked 

 and is evident only in the case of the proximal segments of the 

 first and second, and those of the nineteenth and twentieth. 

 "With the exception o£ those belonging to the last radial element, 

 and the mesial segment of the first, all the proximal and mesial 

 segments are fairly well ossified. The inner portions of the 

 proximal segments are entirely osseous, but towards the middle 

 of the length of each segment a slender axial core of cartilage 

 makes its appearance round which the bone forms a thick layer. 

 From the centre outwards the bone gradually thins away, while 

 the core of cartilage thickens and eventually forms the wholly 

 cartilaginous distal extremity of the segment. The mesial seg- 

 ments are, for the most part, solid bone in the centre, but from 

 this point in either direction an axial core of cartilage appears, 

 and the superficial bones gradually thinning away leaves the 

 two extremities of the segment entirely cartilaginous. 



From 51 to 53 dermal rays are supported by the twenty radial 

 elements, and, as in Acipenser, their deeply cleft proximal 

 extremities embrace the distal, and partially also the mesial 

 segments of the difi'ereut elements. 



Anal fin. — In this fin there are eighteen radial elements, all o£ 

 which are trisegmental. The only indication of concrescence 

 is the fusion of the proximal segments of the first and second 

 elements. In other respects the anal fin is very similar to the 

 dorsal. The number of dorsal rays is approximately forty-nine. 



Amiidje. 

 Amia calva. 

 Dorsal fin. — The long dorsal fin of this G-anoid is supported by 

 a series of forty-nine radial elements, all of which are triseg- 

 mental with the exception of the first two, the fifth, and the last. 

 The first element is represented only by its proximal segment, 

 which at its distal extremity is tipped with cartilage and 

 supports the first dermal ray. The proximal segment of the 

 second supports a small nodule of cartilage which apparently 

 represents a distal segment. The fifth has no proper proximal 

 segment, and consists only of small cartilaginous mesial and distal 

 segments supported by the proximal segment of the sixth. The 

 forty-ninth, or last of the series of ray-bearing radial elements. 



