No. 2.] WHITEAVES — NEW DEVONIAN FOSSILS. 9T 



The few detached plates yet found are rarely perfect, though the 

 sculpture of their outer surface is always beautifully shewu. 



In some respects the Campbellton Coccosteus very closely 

 resembles the C. cusjndatus of Agassiz, but in others there are 

 such marked differences between the two forms that it is thought 

 most prudent, for the present, to distinguish the Canadian species 

 by a local name. No detailed description of C. cusjjidatus has 

 ever been published, and the illustrations that give the best idea 

 of its characters are the figures on plat^ 3 of the " Old Red Sand- 

 stone." Assuming that these figures are essentially correct, the 

 shape of the post-dorsomedian plate of the Campbellton Coccosteus 

 (which Agassiz, who calls it the dorsal plate, regards as offering 

 one of the best specific characters) and that of the diamond shaped 

 ventro-median are almost exactly similar to those of C'. cuspldatns. 

 But on tlie other hand, in many of the plates of C. Acddicus, 

 and especially in some which have not been separately described 

 on account of the uncertainty of their homologies, but which are 

 supposed to be isolated dorso-median plates of exceptionally large 

 individuals, the tubercles are arranged in very distinct concentric 

 lines, with continuous and comparatively broad grooves or spaces 

 between them ; an arrangement not indicated at all, or at most 

 very obscurely, in the figures of C. cuspidafus. Again, the super- 

 ficial grooves on the cranial shield of C. Acadicus are much 

 more like those of C. decipiens as represented in a wood-cut in 

 the '' Foot Prints of the Creator," (third edition, figure 11) than 

 they are like those in the figure of C. ciisjndatus in the " Old 

 Red Sandstone." In the C. Acadicus the most con«^picuous of 

 these grooves are constantly those which run from a to e on 

 the accompanying diagram, and from the centre of each of these 

 lines to the lateral notches at b. b. Making- allowances for dis- 

 tortion, precisely similar grooves are to be seen in Miller's wood- 

 cut of the '• cranial buckler " of C. decipiens, but they are en- 

 tirely absent in his figure of the cranial shield of C. cuspidatus. 

 Further, in the Campbellton Coccosteus other superficial grooves 

 run from e. e. and d. d. to /. /. in sueh a way as to inclose a 

 triangular space on either side, with a wide space between their 

 inverted apices at /. /. This again, is just the arrangement in 

 the ''cranial buckler " of C. decipiens, whereas in C. cuspidatus 

 the apices of the two triangles are not separated by a space bu t 

 connected by a curved, transverse groove. It would seem, there- 

 fore, that the G. Acadicus may be distinguished from C. decipien s 

 Vol. X. G No. 2 



