238 A^'NALs ^^EW york academy of sciences 



than the larger specimen and larger than the other — larger even than the 

 larger of the types, from both of which it appears to be distinguished 

 by having the surface conspicuously roughened over the convex portion 

 but smooth about the margins. The shape is extremel}^ similar to that 

 of the smaller of Ulrich's specimens. This is a highly convex little 

 shell, rather strongly compressed at the ends. 



Griffithides mucronatus sp. nov. 



Head : glabella large, inflated, considerably narrower behind ; basal lobes 

 triangular, small, strongly defined. Neck ring defined from the gtabella by a 

 deep sulcus, strongly arched in the middle with moderately long lateral pro- 

 jections. Eye lappets small, oblique. Border anterior to the glabella, mod- 

 erately narrow, depressed, slightly convex, defined by a groove. Surface ot 

 glabella granulose, much more finely in front than behind. Median portion of 

 neck ring and projecting end of eye lappets also marked by coarse granules. 

 Outer margin of anterior border with fine parallel raised lines. The remain- 

 der of the surface, including the more depressed portions, finely pitted. 



Free cheek with a wide, gently convex border defined by a strong groove. 

 Eye large, prominent, many faceted, bounded below by a curved ridge. Genal 

 angle much produced into an elongated spine. Surface finely pitted, outer 

 margin marked by regular, fine, parallel lirse. 



Thoracic segments nine, strongly lobed, axial portion a little less than one 

 third of the whole. Longitudinally furrowed. 



Pygidium semi-elliptical or shield-shaped, length and breadth about equal. 

 Border broad and gently convex or nearly flat. From its well defined inner 

 margin, the main portion of the pygidium rises abruptly, the axis being also 

 abruptly and strongly elevated above the pleural areas. At its anterior end, 

 the axial and pleural portions are about equally broad, and the border about 

 one half as broad as the three other divisions. In old specimens, the border is 

 relatively narrower. The segments are defined by deep angular grooves. 

 There are 16 on the axis and 9 or 10 on the sides. The lateral segments are 

 sometimes partly divided by indistinct furrows. Besides the number given 

 above, there is a small articulating segment at the front end of the axis, and 

 the anterior of the lateral segments is made double by a groove which divides 

 it into two parts, the posterior having the normal size, the anterior being 

 somewhat smaller. The surface of the lateral segments is rather coarsely 

 granulated, and sometimes the granules are segregated along a raised line. 

 Each of the axial segments is marked by a row of still larger granules. The 

 border is traversed by. a few delicate, inosculating lines and is finely rough- 

 ened. 



This species is abundant in the basal limestone of the Fayettevllle shale, 

 rare and somewhat doubtfully identified in the Batesville sandstone below. 



