Prof. Rcid on the Vog-marus Islandicus. 465 



spinal or interhaemal spines in the turbot {Rhombus maximus) and 

 in the genus Platessa, and probably in all of the Pleuronectida. 

 The tendons of two small muscular bundles, which run parallel 

 to each interspinous or interneural spine, are attached on each 

 side to the bifurcated extremity of the fin-ray embracing the 

 cartilaginous disc. Between these two muscles a thin aponeu- 

 rotic prolongation is sent inwards from the spine. At the an- 

 terior part of the body the interneural spines and the spinous 

 processes of the vertebrae are equal in number, but towards the 

 posterior part of the body where the vertebrae become consider- 

 ably longer, more than one interneural spine is interposed be- 

 tween two spinous processes. The vertebrae varied in length 

 and in their other dimensions in different parts of the spinal 

 column. The first and second — counting from before back- 

 wards — were considerably shorter than those which immediately 

 succeeded them. The longest were placed in the posterior part 

 of the spinal column. The following measurements point out 

 the relative length, and some of the other dimensions of these 

 vertebrae : — 



Breadth. 

 Nearly the same as the height. 



2¥ 



The transverse processes of the dorsal vertebrae were directed 



* It is exceedingly improbable tbat this marked shortening of the bodies 

 of the fifty-ninth and sixtieth vertebrae is their natural conformation, as they 

 were nearly anchylosed by portions of cartilage which took the place of the 

 gelatinous-looking substance occupying these cavities in the other vertebrae, 

 and the cavities tliemselves were considerably diminished -in depth. Va- 

 lenciennes says that in the Trachypterus leiopterus the number of the ver- 

 tebrae is ninety or ninety-one " qui ont cela de remarquable, qu'elles vont 

 toujours en s'alongeant, et mime en s'amincissant, ce qui rend les premieres 

 plus hautes que longues ; vers le milieu elles commencent a devenir un peu 

 plus longues que hautes, et la longueur de celles de I'extr^mit^ posterieure 

 surpasse cinq ou six fois leur hauteur." 



Ann. ^ Mag. N, Hist. Ser. 2. Vol.'m. 30 



