176 ORiaiNAL AETICLES. 



column. They were present in the specimen described by Mr. 

 Groodsir, who mentions tliem as seventeenth and eighteenth vertebrae ; 

 and, in that instance, they appear to have been both in a dii'cct line 

 with the vertebral column. On the other hand, in another specimen, 

 of the tail of which Mr. Groodsir has preserved a cast, the eleven 

 caudal fin rays are placed exactly opposite the corresponding 

 interspinous bones, but in their series there is no cartilage corres- 

 ponding to the end of the vertebral column. In an additional 

 specimen, from which a driii'd skeleton has been, this winter, pre- 

 pared for Mr. Goodsir, by his former pupil, Mr. Eamsay Traquair, 

 who has taken particular care with reference to this point, the 

 caudal rays are of the same number as the interspinous Ijones, but 

 are not placed opposite to their extremities : that which corres- 

 ponds to the interspinous bone immediately below the sixteenth 

 vertebra is placed opposite the extremity of the vertebral column, 

 and its two osseous slips separate, one to join the ray above, the 

 other to join the ray below ; while the extremities of these rays con- 

 verge to a common dermal plate, which obviously consists of at least 

 two fused together. Lastly, Wellenbergh's sketch, taken from a di'ied 

 skeleton, exhibits two fin rays placed closely together opposite the 

 end of the vertebral column, their extremities converging to two 

 dermal plates closely united. 



Muscles of tie Trunk.— {7t. VI. fig. 2). The peculiarity of the 

 develo])mcnt of the muscles of the trunk, consists in the almost 

 total disappearance of all except those of the fins, which are of 

 enormous size. This was first pointed out by Professor Goodsir. 

 Meckel, indeed, describes the muscles of the sun-fish,* but his 

 description is not at all accurate. 



The muscular masses which move the dorsal and anal fins extend 

 upwards and do\vnwards from the middle lateral line. They are 

 both very much stronger at the fore j^art than behind. That 

 belonging to the dorsal fin is prolonged forwards along the whole 

 length of the trimk to the back of the skull ; while that belonging 

 to the anal fin presents an abrupt anterior margin at the back of 

 the abdominal ca\ity. As the middle lateral line is only half as far 

 removed from the dorsal as from the anal fin, and as the two fins are 

 of equal size, the greater vertical space available for muscles of the 

 latter is compensated for by the greater antero-posterior space 

 occupied by those of the former. Behind and in contact with those 

 two sets of muscles, is a fim-shaped arrangement of distinct muscles, 

 ending in tendons, one going to each caudal ray. Here, also, we find 

 that, on account of the position of the middle lateral line, the 

 muscles to the superior caudal rays, take origin diflerently from 

 those of the inferior rays : for, while the latter arise only from the 

 corresponding interspinous bones, and that part of the penultimate 



* Meckel, Comparative Anatomy. French Edition. Vol. v, p. 184. 



