192 Mr Goodsir on certain Peculiarities in the 



ton.* I found that the rays of the tail-fin, and their inter- 

 spinous bones, were crowded together in a direction from be- 

 hind forwards, and abutted against the superior-spinous pro- 

 cess of the fourteenth and the inferior-spinous process of the 

 fifteenth vertebra. The sixteenth, seventeenth, and eighteenth 

 vertebrae assumed the appearance, the two former combined, 

 of an interspinous bone, and the latter of a fin-ray, and could 

 not have been distinguished from these but by their direct con- 

 tinuation with the bodies of the vertebrae, and their more cy- 

 lindrical and shorter form. The joint between the seventeenth 

 and eighteenth was in the line of the articulations of the fin- 

 rays and then' interspinous bones, the ultimate vertebra as- 

 suming the appearance and function of a fin-ray, the penulti- 

 mate and antepenultimate combined of an interspinous bone. 



The interest involved in this form of skeleton consists in 

 the explanation it affords of the true nature of the so-called 

 last vertebra in the spinal column of fishes. Is that fan-shaped 

 bone a vertebra ? or is it a composite bone, containing the ele- 

 ments of a number of vertebrae and of interspinous bones of 

 fin-rays ? I have always been led to conclude that it is a com- 

 posite bone, and it required only such an arrangement of ske- 

 leton as that now under consideration to afford a natural ana- 

 lysis of the tail in this class of fishes, and to prove the correct- 

 ness of the opinion to which I have just alluded. In many of 

 the osseous fishes the last bone of the spine exhibits traces of 

 a central element, and in some families (Tsenioides) it ap- 

 pears to be prolonged far beyond the caudal fin, in the form 

 of a fine filament, but in none, as far as I am aware, is it ar- 

 ranged as in the present instance. 



The next peculiarity is in the muscular system. The sun- 



* Meckel, Comp. Anatomy, French ed„ torn. ii. p. 285. For a drawing 

 of the tail, which appears to have been made from a dried skeleton, see Dr 

 C. A. S. Schultze, Ueber die ersten Spuren des Knochensystems, und die 

 Entwickelung dor Wirbelsaule, in den Thieren, Meckel's Archives, 1818. 

 "Willenbergh's drawing, which, he states, was made from a dried skeleton, 

 is incorrect in the mode of junction of the pectoral girdle to the spine, but, 

 more particularly in the mal-representation of the mode of termination of 

 the spinal column. He has mistaken the two or three last vertebrae for a 

 fin ray and interspinous bone. 



