ANATOMY OF VERTEBRATES. 



35 



not only manifests itself in the double pleur- 

 and neur-apophyses on each side, but in small 

 interneural and interhaemal cartilages, fig. 25. 

 These peripheral cartilages are more feebly 

 developed in Spatularia. 



In the Chimseroicls (Holocephali) the bases 

 of the neur- and par-apophyses of about ten 

 of the anterior trunk-vertebras coalesce and 

 form a continuous accessary cartilaginous 



/ o 



covering of the fore part of the notochord ; 

 and the confluent neural spines here form a 

 broad and high compressed plate. Between 

 the neurapophyses are wedged accessory in- 

 terneural cartilages. 



In NotidanuSyAcanthias, Centrina,and. Scym- 

 nus, the interneurals, fig. 30, z, resemble the 

 neurapophyses, ib. n, inverted, and are in- 

 terposed, like wedges, between them, with 

 the apices reaching the centrum. In Scyttium, 

 Mustelus, Sphyrna, and Carcharias, the in- 

 terneurals resemble the neurapophyses in size 

 and shape, but occupy a position above the 

 intervertebral joint. In Galeus the ( vegeta- 

 tive repetition ' is further exemplified by four 

 stellate points of ossification, one of which is 

 intervertebral ; and above these are rudiments 

 of neural spines. The spinal nerve directly 

 perforates the neurapophysis ; or, when the 

 two roots escape separately, one also per- 

 forates the interneural. The pleurapophy- 

 ses are short and simple cartilages, either 

 wedged into the interspaces of the parapo- 

 physes (Notidanus, Carcharias, Scymnus), 

 or attached to the ends of the parapophyses 

 ( Galeus) of, say, the twenty-six anterior verte- 

 brae. In Acanthias there may be forty pairs 

 of such riblets, fig. 30, pi. 



In the flat Plagiostomes (Skates, fig. 64, 

 Rays, Torpedos) vegetative repetition mani- 

 fests itself in the multiplication of vertebrae, 

 and especially of the central elements ; which, 

 as indicated by their rudimentary ossification 

 in Chim&ra, are commonly more numerous 



D 2 



\ o 



Skeleton of Sturgeon, 

 (Acipenser Sturio). cxiv. 



