NO. 9 NEW CAMBRIAN TRILOBITE FAUNULE — RASETTI 



29 



geniculation of the posterior cephalic border, marked by a short 

 spine, is much closer to the axial furrow than in previously known 

 Eodiscidae. The pygidium, compared with Serrodiscus, has a shorter 

 axis and lacks marginal spines. 



OODISCUS SUBGRANULATUS Rasetti, new species 



Plate 1, figure 4; plate 10, figures 1-10 



Available material. — Several cephala and pygidia more or less 

 completely preserved. 



Description. — Cephalon somewhat widening forward from the 

 genal angle, widest slightly in front of the midlength, well rounded 

 anterolaterally, with almost straight portion of frontal outline. Gla- 

 bella ovate, somewhat pointed in front, not reaching anterior border 

 furrow, strongly elevated above the cheeks, sloping down from pos- 

 terior to anterior end. Occipital furrow barely indicated by a pair 

 of exceedingly shallow lateral depressions, very short (sag.), rounded. 

 Cheeks strongly downsloping posteriorly, gradually flatter toward 

 the anterior part ; no preglabellar depression. Border somewhat con- 

 vex, well defined by border furrow, of even width around the anterior 

 half of the cephalon, narrowing toward the genal angle, bearing two 

 pairs of small, short marginal spines, one pair at the level of the 

 cephalic midlength, a second pair halfway between the first and the 

 genal angle. Lateral border furrow continued into posterior border 

 furrow ; the latter directed outward and forward from axial furrow, 

 curving outward distally, hence as a whole convex forward. Posterior 

 border horizontal in inner third, then sharply downturned to reach 

 the much lower level of the genal angle ; a small, upright spine at the 

 geniculation, usually broken in extracting the specimen from the 

 matrix. Genal angle narrowly rounded. 



Pygidium assigned to the species on the basis of similar shape 

 and identical ornamentation, less convex than cephalon, about paral- 

 lel-sided in anterior half, well rounded posteriorly. Axis widest at 

 the base, not greatly elevated, tapered, un furrowed, occupying two- 

 thirds of pygidial length. Anterior border straight, transverse from 

 axial furrow to geniculation which is relatively close to axial furrow, 

 distally slanted backward and with marked facet, paralleled by well- 

 impressed anterior border furrow; remainder of border furrow and 

 border as in cephalon; border lacking spines. Doublure reflexed in 

 usual manner. 



Cheeks and pleural regions of the pygidium covered with small, 

 sparse granules, of density variable in different individuals. The py- 



