60 



LECTURE III. 



four, two anterior, two posterior, as in the Mullet {Miigil,fig. 16. z) ; 

 sometimes two, as in the Perch, the posterior in this and most other 

 fishes being overlapped by the anterior articulating process of the 

 succeeding vertebra : commonly only the anterior zygapophysis is 

 developed {fig. 17. z), which touches, but rarely overlaps, as in the 

 Polypterus, the neural arch in advance. It is peculiar to fishes to 

 have articular processes developed from the parapophyses ; we have 

 noticed these already in the abdominal region in the Ray ; in the 

 osseous fishes, when present, they are confined to the caudal vertebrce 

 {fig. 18. z'): they are particularly developed, sometimes branched, 



Terminal caudal vertebi-a?, Sword-fish (Xipkias). 



forming a network about the haemal canal in certain species of Tunny 

 {Thynnus, xxiii. i. p. 265.). In Loricaria peculiar accessary pro- 

 cesses are sent out from the neural arch of the seven anterior ver- 

 tebra; which abut against the osseous lateral shields of the dermal 

 skeleton. 



The parapophyses are very short in some fishes (Salmo, Cfupea) : 

 they are longest and most expanded in the abdominal region of the 

 Cod tribe {fig. 19. p), where they support the air-bladder, which in- 

 timately adheres to their under surface, and, in one species of Gadus, 

 sends processes into expanded cavities of the parapophyses, thus fore- 

 showing the pneumatic bones of birds. They gradually bend down 

 near the tail, where they form, as in all fishes, the liasmal canal. 



The pleurapophyses of fishes correspond to what are usually 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. 23.), their distal ends are not connected with any bones 

 analogous to sternal ribs or sternum ; i. e. the abdomen is unclosed 

 below by the crura and spines completing the hajmal arch. The 

 true homologues of sternal ribs or abdominal hoemapophyses re- 

 tain the primitive aponeurotic tissue, and may be well seen in the 

 Bream, extending from the ends of the vertebral ribs. These elements, 



