in the Neighbowhood of Edinburgh. 217 



as well as the head of the Megalichthys of Leeds, that the iden- 

 tification will not be insurmountable. 



This relic Was the first which I discovered at Burdiehouse ; 

 for which reason I have requested M. Agassiz, that, in its specific 

 name, I may be allowed to dedicate it to a geologist for whom I 

 possess the greatest esteem. He has accordingly obliged me by 

 sanctioning the name of Pygopterus Bucklandi. 



M. Agassiz conceives that the best specific character of the 

 Pygopterus Bucklandi is the relative smallness of its scales. 



SECTION XIV— THE REMAINS OF THE FISH OF THE PLACOIDIAN ORDER 

 DISCOVERED AT BURDIEHOUSE. 



It has been explained, that Placoidian fish are easily known on 

 account of the irregularity manifested by the solid parts of their 

 integuments, which consist of materials of enamel sometimes con- 

 siderable, and sometimes reduced to little points ; as is shewn in 

 the tubercles of Rays, or in the different chagrins of Squali, &c. 



The same naturalist, at the commencement of his great work, 

 has expressed his imperfect knowledge of the fossil fish of this 

 order. But I believe that since his recent visit to Great Britain, 

 he has been enabled to examine some few specimens in compara- 

 tively a better state of preservation. He conceives, that, in cor- 

 respondence with differences of organization, such remains of fish 

 as are found in beds anterior to the carboniferous group, would 

 have to be referred to the order of Placoids. 



M. Agassiz has recently stated, that, among the Placoids, 

 those above all predominate which have their teeth furrowed in 

 both the external and internal surface, and have large thorny rays. 



These large rays are now considered as the supports of the 

 dorsal fins of several genera, which, from their approach to the 

 Cestracion of New Holland, M. Agassiz has formed into a dis- 

 tinct family, under the name of Cestraciontes, jto which family six 

 fossil genera, approaching to the Squalus, with rays differing con- 

 siderably from each other, have been already assigned. 



VOL. XIII. part i. e e 



