PAPERS OX GEOGRAPHY AND GEOLOGY 339 



ture was capable of great speed, for back of the head 

 there are the rays of powerful fins. You might ask what 

 use this fish had of crushing teeth, and the answer would 

 be that perhaps it fed on the water fleas and other shelly 

 creatures that would require this form of dentition. 

 Such teeth assumed a decided variety of shapes, and it 

 would be easy for one if he met them separately to as- 

 cribe them to different species. 



There were still other shark forms and there are in- 

 dications that these also were of large size. Their re- 

 mains are, however, so scattered that it is hard to frame 

 a definite idea of their outlines. I found, for instance, a 

 finely ornamented spine eight inches long that must have 

 extended a considerable distance above the back. It has 

 ridges running its full length and along these there are 

 strings of little black knobs. As one looks at this speci- 

 men he can almost imagine a hungry shark with its dorsal 

 or top fin attached to this ornamental spine cleaving the 

 water, in zealous pursuit of its prey. 



The tubercles that abound in the integument of cer- 

 tain sharks are frequent and are found at times in con- 

 siderable number, clusters or masses. These are star- 

 shaped with a raised center and with a base about a quar- 

 ter of an inch in diameter. 



Then there are other sharks that had numerous spines 

 in the integument. Formerly I thought that these spines 

 must be solitary, placed for instance on the backbone, but 

 more recently I have found a large specimen that would 

 indicate that they might have been scattered over the 

 shark and in all stages of development, ranging from 

 those shaped like a small v to those with three ribs and 

 those of more up to a dozen, all apparently secured in the 

 integument and so forming quite a defense. These or 

 similar spines have occasionally a length of three to 

 four inches, while still others, evidently of a different 

 genus, are of a tapering spindle-like shape. 



Some have tried to connect up these spine finned fishes 

 with the Port Jackson shark, and they may be right but 

 there is still need of light. They must have ranged from 

 those small to those of large size, if the spines are any 

 criterion. There is nothing to show what the dentition 



