91 



as crushing JMlrniliMll, progiMrively diminish in siie, while at Uio same time the number 

 composing each row drm-am. From the oblique uul apparently fpirml disposition of thr 

 rows iif til-ill, tin ir >v mini-triad arrangement on the opposite sides of thr jaw, and llu-ir gra- 

 iliiatrd dircniity of fonn, tliry coiwtitute the most elegant tessellated covering of thr jawi 

 which is to be met with in thr whole class of Pishes. By the modifications of the form of 

 the teeth above described, the anterior ones are adapted for sriziiig and retaining, and tin- 

 posterior for cracking and crushing the animal* that become the prey of the Ctttracion, and 

 which chiefly consist of the shell-clad Mollusks and Crustaceans. 



Hunterian. 



Family NotidanifUe. 



388. A portion of one of the jaws of a Shark (Notiilamis grist**). 



The number of recumbent or successions! teeth does not exceed two behind each tooth in 

 place : the asygous symphysial tooth deviates considerably from the typical form of the teeth 

 in this genus, as do likewise the small teeth at the extremities of the jaw. 



PrttCHted by Dr. Leach, F.L.8. 



Family Sptnacidte. 



389. The skeleton of the Piked Dog-fish (Spina* Accattkiat). The number of ver- 



tebrae is 110, of which 34 support short ribs. Mint. Soutk. 



390. A considerable proportion of the vertebral column of a Piked Dog-fish (Spiiuu 



Lateral sections have been removed from the anterior of some of the middle vertebne, to 

 show the form of the concave articular extremities of the bodies, and the intervening osseous 

 texture. The iuterneural plates equal the true neurapophyses in sice ; these are perforated 

 at their base. 



Hunierian. 



391. A portion of the vertebral column of a smaller Piked Dog-fish (Spimax Aeon- 



fAia*). Htmtfrian. 



392. The maxillary and mandibular arches of a Piked Dog-fish (Spintu Acanthiat). 



The teeth are alike in both upper and lower jaws ; they are thin triangular plates with the 

 apex inclined backwards, so that the anterior edges are opposed to each other ; the enamel 

 does not terminate below in a horizontal line, but is continued along the middle of the bony 

 base. 



by Prof. Owen, F.R.8. 

 I 



