1s;ty-l<<h>. No.33.] UPPER DEVONIAN FISH REMAINS. 31 



tliat it is possible to use them for comparison. In PI. TV. fig. 2 I have 

 given a greatly enlarged photograph of tin 1 sculpture of one of the large 

 median body plates. In this picture we can clearly see that the points 

 of the denticles are situated peripherally, and that therefore their rihs 

 are longer and more powerful on one side than on the other. TRAQUAIU'S 

 description of these denticles simply as "stellate tubercles" does not 

 therefore give the right idea of their form. We further see that the 

 denticles are rather distant and placed somewhat irregularly. However, 

 I assume that the denticles are considerablv closer to each other than 



*s 



appears from the illustration. Between the typical ribbed denticles we 

 see round dark spots and these I consider to be denticles that have 

 been torn off by the violent mechanical preparation. As is known, 

 these fossils are brushed out of the schists by the aid of a metal brush, 

 which on the whole cannot be particularly favourable for the preserva- 

 tion of the finer degrees of sculpture. 



I have given so thorough a description of the sculpture on the large 

 median body plates because it is of importance for the comparison! with 

 Psammosteus remains. It would take up too much space to go through 

 ail the variations that the sculpture of Drepanaspis undergoes on the 

 various body plates, scales and fulcra. 



TRAQUAIR'S description of the dermal plates, their arrangement, the 

 caudal part, and the general form of the body, is so exhaustive that 1 

 cannot add anything of special importance. There is however one point, 

 in which I am quite at variance with him, and that is his views of 

 the dorsal and ventral sides. In this respect I agree with BASH- 

 FORD DEAN 1 who in his review of TRAQUAIR'S work on Drepanaspis 

 puts forward the opinion that TRAQUAIR had confused the dorsal and 

 ventral sides. As far as I can understand, DEAN'S argument has not 

 been disproved by the new observations put forward by TRAQUAIR in 

 his supplemental work.- 



I believe this to be apparent from the following. 



In his main work on Drepanaspis, TRAQUAIR summarises his 

 views of the systematic position of this form in the following way: 



"These characters assign to Drepanaspis a place in the Oslfi- 

 codermi, and its indubitable resemblance to Pteraspis leads us to clas: 

 it in the Heterostracous subdivision, although evidence from microscopic 



i Science N. S. Vol. XIX, No. 471, 1904. 



- Supplement to the Lower Devonian Fishes of Gemttnden. (Transactions 

 Soc. Edinhurgh, Vol. XLI, 1905, y. 469). 



