2910 SHARKS AND RAYS 



yellowish white beneath. It is very abundant on the British coasts, sometimes 

 making its appearance in such incredible numbers that upward of twenty thousand 

 were once captured in a single haul on the Cornish coast. In common with an 

 allied species {A. blainvillei ) , this dogfish presents the peculiarity of inhabiting 

 the two temperate zones but being unknown in the intervening tropical seas. 

 The eggs are hatched within the body of the female, and a considerable num- 

 ber of young are produced at a birth. Somewhat dangerous wounds result from 

 the spines. 



Among other types, we may notice the genus Centrophorus, repre- 

 sented by eight European species, and a ninth from the Moluccas, all 

 of which differ from the last by the upper teeth being erect and spear-like, with a 

 single cusp; the dorsal spines being often very small. Apparently not exceeding 

 five feet in length, these sharks are noteworthy on account of the depth at which 

 they live, one of the species being caught with lines at a depth of from three to 

 four hundred fathoms off the coast of Portugal. When hauled up, these fish are 

 quite dead, owing to the diminished pressure. A fossil species occurs in the Chalk 

 of Syria. In the typical genus Spinax the teeth in the two jaws are likewise dis- 

 similar; but those of the lower one are broader than in the last, although with the 

 points similarly turned aside. The genus is now represented by three small species 

 from the -Atlantic and the extremity of South America; but has been recorded from 

 the Miocene Tertiary. The Greenland shark (Lcemargus borealis) of the Arctic 

 seas, which occasionally strays as far south as Britain, represents another genus 

 characterized by the small size of all the fins and the want of spines to the dorsals, 

 the first of which is situated considerably in advance of the pelvic pair; the skin 

 being uniformly covered with small tubercles. In the upper jaw the teeth are 

 small, narrow, and conical; but those of the lower jaw, which are numerous and 

 form several series, have their points so much bent to one side that their inner 

 margins form the cutting edge, which is not serrated. Growing to a length of fif- 

 teen feet, the Greenland shark is a determined enemy to the right whale of the same 

 seas; and when feeding on the carcass of one of those mammals becomes so intent 

 on its occupation as to allow itself to be harpooned without attempting to escape. 

 Four living young are stated to be produced at a birth. Finalty, we have the spiny 

 shark (Echinorhinus spinosus] of the Mediterranean and Atlantic, which while agree- 

 ing with the last in the small size of the fins and the absence of spines to the dor- 

 sals, differs by the teeth being alike in both jaws, and by the presence of large 

 rounded tubercles scattered over the skin; the body being very bulky, and the tail 

 short. This shark lives at considerable depths, and but rarely comes to the sur- 

 face. 



THE EXTINCT PETALODONTS Family PETALODONTID^E 



The extinct genera Petalodus andjanassa, together with several other allied 

 types from the Carboniferous rocks, represent a family apparently connecting the 

 last with the more typical rays. In these fishes the body is moderately depressed, 



