CENTRING. CENTRINA. 145 



reached abruptly : there are some which_, by having no 

 spines^ evince an affinity to Galeus; while, from being 

 destitute of an anal fin, they come within the confines 

 of the present group : these form Cuvier's sub-genus 

 Scymnus, which we shall, at least for the present, keep 

 entire, since the divisions that have been made of it 

 appear to us * too slightly marked for even sub-generic 

 separation ; more especially as there are evidently fi^ve 

 divisions, with much more prominent characters, enter- 

 ing into this genus. Scymnus seems to represent Se- 

 Ulceus in some particulars well worth noticing. To 

 Dr. Scoresby we are indebted for all the knowledge we 

 possess of the habits of S, borealis, an immense species, 

 observed by that well-known navigator and philosopher 

 in the Arctic seas. According to his observations, it 

 often grows to the length of fourteen feet, and six or 

 eight feet in circumference. Its chief food is derived 

 from dead whales and other Cetacea, out of which, at a 

 single gripe, it scoops masses of blubber as large as a 

 man's head : hence it is, that when, on such occasions, 

 any sailors may be in the water engaged in securing the 

 whale, this shark is so intent upon claiming his portion, 

 that he offers no molestation to the fishermen ; indeed, 

 he is so ravenously fond of blubber, that he has been 

 known to return to the carcase, even after a long knife 

 has been run into his body by the seamen engaged in 

 cutting up the whale. The slight variation in the teeth 

 of tliose species which we place in this sub-genus, seems 

 to mark the transition from the last genus. In Galeus, 

 the teeth in both jaws are serrated on the external edge, 

 and inclined outwards ; but in Scymnus, the upper teeth 

 are straight and narrow, while those in the lower jaw are 

 crooked, pyramidal, and equilateral : between these, 

 however, are species having the upper teeth of Scymnus, 

 and the lower ones of Galeus. 'From Scymiius we pass 

 to one of the typical genera, both of which have the 

 dorsal fins spined: the first is Centrina, which, as 



* Laemargus M. and H., Echinarrhinus Blainv. 

 VOL. I. L 



