Dr. R. H. Traquair on Palceozoic Fishes. 371 



which the specific name prumensis may be given, belongs to 

 the genus Acanthaspis of Newberry, which was supposed by 

 its founder to be related to the Cephalaspidae *. Mr. Smith 

 Woodward, however |, in describing an apparently allied 

 form from Spitzbergen, A. decipiens, inclined to the belief 

 that the genus was most nearly related to the Asterolepidge, 

 and that the spine, here fixed and immovable, represented 

 the articulated pectoral limb of Asterolepis or Pterichthys. But 

 from the resemblance of the plate and spine to the correspond- 

 ing parts in Phlyctcenaspis, I cannot doubt that, whatever 

 A. deciptens of Smith Woodward may be, Acanthaspis armata 

 of Newberry is a Coccostean \. 



CARBONIFEROUS. 



Cestraciontid.se. 



EUPHYACANTHUS, gen. nov. 



Dorsal spines with a few longitudinal ridges on the ante- 

 rior aspect, which, at the apex, likewise cover the sides. 

 Two rows of recurved denticles on the posterior area, within 

 the angulated margins by which the latter is bounded. 



This genus resembles Tristychius, Agassiz, save in the 

 position of the denticles, which are within and not on the 

 limiting margins of the posterior area. 



Euphy acanthus semistriatus, sp. n. 

 (PI. IX. figs. 2-6.) 



These spines (PI. IX. figs. 2 and 3) attain sometimes a 

 length of 5^ inches. When the apex is preserved unabraded 

 it may show four or five ridges extending over its sides, but 

 as we pass downwards these become limited to the anterior 

 aspect, leaving a bare space between them and the postero- 

 lateral margin. Towards the base of the exserted portion of 

 the spine there may be a variable number of these ridges on 

 each side of the anterior and median marginal one — two, 

 three, four, or more — and the number is sometimes increased 

 by intercalation. The posterior area shows a median groove 

 (tigs. 4 and 6), on each side of which, but within the margin 

 separating the area from the side of the spine, is a row of 

 rather small, sharp, and strongly recurved denticles (tig. 5). 

 Two forms of this spine are observable — one straight, more 

 tapering, and with fewer ridges (fig. 2), and a second, stouter^ 



* Geol. Surv. Ohio, vol. ii. pt. ii. (1875) p. 37, pi. lv. figs. 1-6. 



t Ann. & Mag-. Nat. Hist. (6) vol. viii. pp. 4-6. 



j K. H. Traquair in Geol. Mag. (3) vol. x. 1893, p. 149. 



