ANATOMY OF VERTEBRATES. 39 



pophyses,' fig. 43, h, forming the haemal arch in the tail, and 

 coexisting there with par- and pleur-apophyses, ib. p, and pi. 



The pleurapophyses of fishes correspond to what are termed in 

 Comparative Anatomy, ' vertebral ribs,' and in Human Anatomy 

 ' false or floating ribs : ' for, with few exceptions, of which the 

 Herring is one, fig. 37, their distal ends are not connected with 

 any bones analogous to sternal ribs or sternum ; i. e. the abdomen 

 is unclosed below by the osseous parts completing the haemal arch. 

 The true homologues of sternal ribs and sternum retain the primitive 

 aponeurotic texture, and may be well seen in the Bream, ex- 

 tending from the ends of the vertebral ribs. These elements, or 

 pleurapophyses, figs. 31, 32, pi, are usually appended to the 

 extremities of the parapophyses, p, the articulation frequently pre- 

 senting a reciprocal notch in each. But, in some bony fishes, as 

 Platax, the ribs articulate with the bodies of the vertebrae, in de- 

 pressions behind the parapophyses ; and in Polypterus beneath the 

 parapophyses, as in the cartilaginous Heptanchus, Carcharias, and 

 Alopias. 



Between the floating ribs extends an aponeurosis, the remains 

 or homologue of the primitive fibrous investment of the abdomen 

 in the Lancelet and Lamprey. In the Salmon and Dory the ribs 

 continue to be attached to some of the parapophyses after they are 

 bent down, as in the Amia and Tunny, to form the haemal canal 

 and spine in the tail. The costal appendages of the first vertebra of 

 the trunk are usually larger than the rest, and detached from the 

 centrum ; at least if we regard as such the styliform bones which 

 project from the inner side of the scapulae, and which have been 

 described as coracoids (Cuvier), and sometimes as displaced iliac 

 bones (Carus) : by the muscles attached to these styliform bones 

 the succeeding ribs are drawn forward and the abdomen expanded 

 in the Cyprinoids. Pleurapophyses are entirely absent in the 

 Sun-fish, Globe-fish (Diodon), the Tetrodon, the Pipe-fish (Fistu- 

 laria and Syngnathus), the Lump-fish and the Angler. Of all 

 osseous, or rather semi-osseous, fishes, Lophhis presents the simplest 

 vertebral column : the abdominal vertebrae are not only devoid of 

 ribs, but have the feeblest rudiments of parapophyses. The bodies 

 of the vertebrae interlock at their lower and lateral parts by a short 

 angular process fitting into a notch in the next vertebra ; the lower 

 border of this notch represents the lower transverse process in 

 other fishes : it is obsolete in the anterior abdominal vertebrae ; 

 begins to appear about the middle ones ; shows its true character 

 in the tenth ; and elongates, bending downward, backward, and 

 inward, to coalesce with its fellow, and form the haemal arch at 

 the twelfth or thirteenth vertebra, from which the haemal spine is 



