Description of new Palaeozoic Fishes. 191 



doubt that they represent the oldest and most gigantic mem- 

 ber yet known of the ray family. 



Aech^eobatis gigas. (n. sp.) 



Teeth numerous, nearly flat, forming rows from front to rear, and 

 dimishing in size from the second backward ; all quadrangular in form, with 

 the longest diameter transverse ; largest six inches wide by four inches from 

 front to rear ; thickness of the largest teeth, one inch and a half. The cor- 

 rugation of the surface is strong and very regular, resembling that on the 

 teeth of Rhina ancylosiomus, and doubtless had the same function, — to pre- 

 vent objects from slipping while being crushed. 



From the Lower Carboniferous Limestone, (St. Louis Beds), 

 Greencastle, Indiana. 



Collected by Rev. H. Hertzer. 



DlNICHTHYS MINOR. (n. Sp.) 



Dorsal plate four to five inches long, shield-shaped, terminating anteriorly 

 in an obtuse, posteriorly in an acute point ; the sides, irregularly rounded, 

 form a feather-edge, probably buried in the integument. Upper surface 

 gently arched, marked by several obscure longitudinal striae, and by a 

 peculiar transverse crape-like wrinkling. The under surface is uniformly 

 excavated, and arched transversely on either side of the low and sharp 

 central crest This crest is prolonged into a narrow neck-like process, which 

 projects forward and downward from the margin of the shield, and is exca- 

 vated in a broad furrow on its upper surface. 



The supra-occipital bone is wedge-shaped and truncated forward, rounded 

 behind, with a low point at the center of the margin. The upper surface is 

 marked with characteristic transverse, crape-like wrinkling ; the under sur- 

 face slopes backward from the middle, with a prominent ridge which forms 

 the terminal point ; anterior to this slope is a semi-elliptical excavation, 

 divided at bottom in two by a longitudinal ridge. 



An imperfect jaw found with the dorsal plate, and corresponding in size, 

 is about four inches in length, posterior extremely spatulate and thin, the 

 anterior portion polished without, and terminating above in a sharp edge ; 

 the anterior extremity is broken away . 



From the Huron Shale, Sheffield, Loraine Co., Ohio. 

 Discovered by Jay Terrell, Esq. 



CTEN ACANTHUS COMPRESSUS. (ll. Sp.) 



Spine of medium size, perhaps six inches long, much compressed, by one 

 inch and a half wide, strongly arched above ; anterior margin smooth, 

 posterior flattened, with a well-marked rounded ridge along the central 

 line. Upper half of posterior face thickly set with conical recurved teeth. 



