262 ROYAL SOCIETY OF CANADA 
in 1881. In these shields the present writer was unable to trace out 
the sutures, or to satisfactorily determine the shape and arrangement 
of the plates of which the shield is composed. At the time that the 
species was described, it was supposed that these plates would probably 
prove to be like those of a typical species of Coccosteus, such as C. 
decipiens. The supposed outlines of the sutures that are indicated by 
dotted lines in the diagrammatic text figure of C. Acadicus in the 
“Canadian Naturalist,” and in the “ Transactions of the Royal Society 
of Canada” are now known to be incorrect, but the artotype figure of 
the cranial shield of that species in the last named publication is both 
correct and characteristic, as far as it goes. 
With their abundantly additional material Dr. Traquair and Dr. 
A. Smith Woodward have fortunately been much more successful, and 
have made many important additions to our knowledge of this genus, 
and of its typical species, as will be seen by the following extracts from 
their publications thereon. 
In the Geological Magazine for January, 1890, the genus Phlycte- 
naspis was first described by Traquair, as follows, under the name 
Phlyctenwus. 
“ Phlyctænius, nov. gen. Ph. Acadicus, Whiteaves, sp.—On exami- 
ning several pretty good specimens of this curious Coccostean, named 
by Mr. Whiteaves Coccosteus Acadicus, I find that it exhibits certain 
characters which are neither in accordance with those of the genus 
Coccosteus, nor with Mr. Whiteaves’s diagram of its cranial shield. 
Allied to Coccosteus it is, as the arrangement of the sensory grooves, 
correctly indicated in Mr. Whiteaves’s figure, clearly shows. But the 
sutures between the bones are only seen with the greatest difficulty; 
indeed, Mr. Whiteaves admits that the dotted lines in his figure only 
represent their “ supposed outlines.” Accordingly, he has indicated by 
means of those dotted lines certain plates having the same general 
outline as the median-occipital, lateral occipital and central plates in 
Coccosteus decipiens, Ag., whereas the real outline of these plates seems 
to me to be very different. The median-occipital, instead of being 
trapezoidal, with long posterior margin, shorter anterior one, and con- 
vergent sides, appears elongated and five-sided, there being an anterior 
acute angle which is received in a notch between the two centrals in 
front, which are themselves also elongated and more or less of a six- 
sided contour. Laterally, the external occipital, marginal and post- 
orbital may be easily made out, and I think the preorbitals are also 
apparent enough. The orbital portion of the shield (— the part 
between the letters d and e in Whiteaves’ figure) are rather more 
anterior and look more forward than in Coccosteus. None of our 
‘ 
