834 REPORT OF COMMISSIONER OP FISH AND FISHERIES. [88] 



as shown by Franque. Huxley's figure and description show that the 

 notochord, enveloped by cartilage, extends upward toward the dorsal 

 border of the tail. In all the adults examined by me the termination of 

 this compound rod is considerably nearer the dorsal border than is in- 

 dicated by Huxley's figure, and presents a rather broad and but slightly 

 rounded tip, with a central depression corresponding to the neural or 

 spinal canal. Here ends the distinct cartilage. Posterior to it, and be- 

 tween the two laminse of the twenty-first or twenty-second fin-ray (count- 

 ing from below), is a tract of gelatinous matter, which KoUiker, as quoted 

 by Dum^ril, seems to have regarded as the prolongation of the noto- 

 chord. I have been unable to detect any difference between this and 

 the tracts of gelatinous matter between the laminaB of the other caudal 

 fin-rays. 



"But that it may fairly be regarded as the prolongation of the noto- 

 chord, degenerated, and ijot enveloped by a cartilaginous sheath, is 

 rendered at least probable by the following considerations : 



"1. The condition of things in the adult Lepidosteus, as described and 

 figured by KoUiker and myself; the notochord with its cartilaginous 

 sheath forming a slender tapering rod, extending between the halves of 

 fin-rays to the junction of the middle and hinder thirds of the tail. 



" 2. The existence of an undulation of the dorsal border of the tail of 

 Amia corresponding with the termination of the supposed notochord. 



"3. The greater distinctness of this undulation in young individuals." 



This interesting paper concludes with remarks upon " transforma- 

 tion" and "variations in the shape of the tail." 



Counting the one from which the urostyle springs, Micropterus reck- 

 ons thirty-two vertebrae in its spinal column, fifteen of which are ab- 

 dominal. These latter all support each a pair of ribs, which in their 

 turn, all save the last four pair, have epipleural appendages. The atlan- 

 tal pair articulate with the vertebra at the very base of the neural arch, 

 but as we proceed backwards they gradually recede from this posi- 

 tion so as to finally spring from beneath the transverse processes on 

 the under side of the vertebra. This condition is characteristic of a 

 great many of the osseous fishes. The neural and hemal arches of this 

 form are completely anchylosed with the vertebral elements, and in the 

 best developed segments, both superior and inferior, post- and prezyga- 

 pophyses are present. 



The arrangement of the osseous fin-rays and interspinous bones in 

 Micropterus differs somewhat, to be sure, from the arrangement of these 

 parts in Amia, but not at all from what we have known to exist so long 

 in Teleostean fishes, as in Perca for example. 



Thus we see it is, that although the Ganoid Amia calva has in its 

 skeleton many of the characters in common with the highly specialized 

 forms as the Teleosteans, it is, on the other hand, still stamped with 

 characters, more particularly in its vertebral column, of a veritable 

 paleoichthyic type. 



