ZOOLOGY. 627 



ously seem to claim the highest post. At some later 

 period the principle may probably be discovered where- 

 upon their union with the higher Osseous fishes depends. 

 Both are at all events Abdominales. 



Eleventh Class. 



Myozoa, Rhinozoa Reptilia. 



3542. Body entirely naked or covered with scales, 

 with distinctly separate and red-coloured muscles ; two 

 nostrils permeable throughout. 



As the Muscular system is here the characteristic 

 organ, it must be regarded principally in the division of 

 the present class ; the limbs also exhibit nowhere so great 

 a variety as in this class, since they are in some cases 

 wanting, while in others two only, in some four, are pre- 

 sent. In place of fin-rays true toes have, however, made 

 their appearance, these again indicating the greatest 

 variety in the number of the joints ; but meanwhile 

 there are in no instance more than five toes. 



The osseous system is constructed after the pattern of 

 that of the Thricozoa, and is never furnished with dorsal 

 rays as in Fishes. 



The dental formula begins also to be regular. The 

 teeth stand usually in the superior intermaxillary bone, 

 and are sometimes pointed, at others obtuse ; in the Ich- 

 thyosauri and Crocodiles they are even inserted by gom- 

 phosis, as in theThricozoa. In many Serpents additional 

 kinds of teeth occur, namely, the curved poison-teeth or 

 fangs, which have an involuted groove traversing their 

 concavity. In most Reptiles teeth also occur upon the 

 palatal, but there are no longer any upon the lingual bone. 

 In the Chelonia or Tortoises the teeth are entirely want- 

 ing, and they are also scarcely indicated in the Asqua- 

 mous Salamanders and Progs. 



The os quadratum is found as in Birds ; in Serpents, 

 however, the mastoid bone has been freed, and hence the 

 capability possessed by these creatures of expanding the 

 mouth. 



