Dr. R. II. Traquair on Palceozoic Fishes, 371 



w'liicli tlie specific name prilmensis may be given, belongs to 

 the genus Acanthaspis of Newberry, which was supposed by 

 its founder to be related to tlie CephalaspidjB *. Mr. Smith 

 Woodward, however "■■, in describing an apparently allied 

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

 that the genus was most nearly related to the Asterolepida3, 

 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 rhlyctcenaspis, I cannot doubt that, whatever 

 A. deci])itns of Smith Woodward may be, Acanthasjjis anuata 

 of Newberry is a Coccostean \. 



CARBONIFEROUS. 



Cestraciontidse. 



EUPHYACANTHUS, gen. nov. 



Dorsal sj)ines 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 tlie latter is bounded. 



This genus resembles Trii^tychius, Agassiz, save in the 

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

 limiting margins of the posterior area. 



Euyliy acanthus semistriatus^ sp. n. 

 (PI. IX. figs. 2-^) 



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

 length of b\ inches. AVhen 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 

 (Hgs. 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 (fig. 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. Iv. figs. 1-6. 



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



X R. H. Tra(iiiair in Geol. Mag. (3) vol. x. 18'J3, p. 149. 



