CLELAND ON THE ANATOMY OF THE SHORT SUN-FISH. 175 



vertebra, wliicli itself looks like an interspinous bone. Each 

 iuterspiuous bone is connected distally with a little mass of cartilage 

 marked by a groove for a tendon; and these masses are joined 

 together by a thin cartilaginous thread : the uppermost and lower- 

 most are also joined, in the same way, to the great cartilages suj)- 

 portiug the dorsal and anal fins ; and the chain is completed by a 

 similar little mass coiTcsponding to the tip of the last vertebra, 

 joined to the masses above and below it, and differing from the 

 others only in not being gi-ooved for any tendon. Each caudal ray 

 consists of a broad conical cartilage in contact wdth the cartilage 

 terminating the corresponding interspinous bone, on each side of 

 which springs a slender osseous sli^), which comes in contact with its 

 neighbour of the opposite side, and pursues its way through the 

 dense integument, to terminate opposite one of those hard plates 

 w^hose structure has been already described. As the dorsal, caudal, 

 and anal fins are continuous, this mode of termination of the rays of 

 the latter affords the only definite line of distinction between them 

 and those of the former. Either from neglecting this circumstance, 

 or from a variation of the number in different specimens, Welleu- 

 bergh has allotted thirteen rays to the tail. 



Lying in the same range as the cartilaginous bases of the fin rays, 

 and differing from them only in being broader at the point, and 

 having no osseous ray, there is, in the specimen from w^hich I 

 describe, a cartdage corresponding to the end of the vertebral 

 column (Pt. V. fig. 1, i.) ; and notwithstanding that it has no osseous 

 ray, there is a small hard plate opposite it in the margin of the tail. 

 This cartilage and the smaller one which supports it are not placed 

 quite opposite the extremity of the sixteenth vertebra, but are 

 displaced sHghtly upwards, resembling, in this respect, the upwardly 

 inclined last vertebra of other osseous fishes. The claims of these 

 two cartilages to be grouped with the chain of vertebrae, ajjpear to 

 me to be indisputable. In that case the smaller cartilage must be 

 looked on as an intervertebral disc. 



However we may theorize on the matter, the facts are these : 

 that if we pass the eye backwards along the vertebral coliunn, we 

 find the two cartilages in question continuous with the series of 

 bodies of vertebrae ; while if we pass the eye from the dorsal, round 

 by the caudal, to the anal fin, we find that the sixteenth vertebra lies 

 in the series of interspinous bones, that the succeeding cartilage 

 forms part of the continuous cartilage on which the interspinous 

 bones abut, and that the terminal cartilage Kes in the series of 

 cartilaginous bases of fin rays. The importance of these peculiar 

 arrangements, as tending to throAV light upon the structiu'e of the 

 fan-shaped bone which terminates the spinal column of most fishes, 

 is noted by Professor GoodsLr, in his paper already referred to. 

 But perhaps the most curious and important point, as exhibiting how 

 great is the amount of variation possible among individuals of one 

 s])ecies, is the inconstancy of the cartilages terminating the spinal 



