368 Messrs. Hancock & Atthey on Reptile- and Fish-Remains 



spines are very similar to, but they seem to be smaller than, 

 those of the other species, as pointed out by Sir P. Egerton ; 

 they also appear to have the surface more elevated and 

 rounded. 



From the character of the scales and great size of the pec- 

 toral spines, but more particularly from the difference observed 

 in the teeth, we consider ourselves justified in dividing this 

 from the A. Wardi, and beg to dedicate it to Sir P. Egerton, 

 who was the first to point out the probability of its specific 

 distinctness. We therefore propose for it the name of Acan- 

 ihodopsis Egertoni. 



Gyracanthus ttibercidatuSy Agassiz. 



The gigantic spines of this little-understood fish occur 

 pretty frequently at Newsham and Cramlington in a fine state 

 of preservation. In conjunction with Mr. J. W. Kirkby, one 

 of the authors of this paper pointed out in 1863 that these 

 spines were not, as usually thought, dorsal, but were paired 

 spines, most jDrobably pectoral *. We have now before us 

 seventy-one of these formidable weapons ; and the first thing 

 that strikes the observer is, that by far the greater number 

 have lost the apical extremity, and that they are not merely 

 bent from front to back, but are also laterally curved. On 

 closer examination it is found that there are as many bent to 

 the right as to the left side, and that of such bent spines there 

 are just twenty-four pairs. Thus twenty-three spines are left 

 unaccounted for ; these may be considered straight, being bent 

 only from front to back, and their points are entire. But first 

 respecting the paired spines : we have said that they have all 

 lost their points ; they are not fractured, however, but are all 

 worn smoothly down diagonally at a very acute angle ; and, 

 what is still more interesting, this wearing always takes place 

 at the side opposite to that of attachment. Assuming, there- 

 fore, that these spines are pectoral, and that they were inclined 

 backwards and downwards, as assuredly they would be, then 

 the wearing of the points is exactly such as would take place 

 oy their coming in contact with the ground. And, again, the 

 largest or oldest spines are uniformly the most worn ; some, 

 indeed, are reduced to mere stumps. In one such specimen 

 now before us, which is seven inches in circumference, and 

 which must have been one of the very largest, only ten and a 

 half inches are left. Another examj^le, six inches in circum- 



* See paper entitled *' Fish-Eemains in the Coal-measures of Durham 

 and Nortluimherland," by Messrs. T. Atthey and J. W. Kirkby, read in the 

 Geological Section at the Newcastle Meeting of the British Association. 



