NO. 9 NEW CAMBRIAN TRILOBITE PAUNULE — RASETTI 3I 



Types.— Uolotype: U.S.N.M. 146018. Paratypes: U.S.N.M. 

 146019. 



OODISCUS, species undetermined No. 1 

 Plate 11, figures 8-11 



Available material. — A few pygidia, of which two well preserved. 



Description. — Axis very prominent, un furrowed, slightly tapered, 

 rounded posteriorly, not reaching the posterior border furrow. Pleu- 

 ral regions convex and downsloping. Anterior border with genicu- 

 lation relatively close to axial furrow and well-developed facet. Bor- 

 der furrow wide, relatively shallow. Border flat, rather wide. Anterior 

 angles of pygidium sharp. Doublure sharply reflexed, apparently 

 with smooth margin. Length of largest specimen 8.2 mm, width 8.0 

 mm. Surface of test smooth. 



Occurrence. — Collection cs-4, North Chatham. 



Discussion. — This pygidium seems definitely to belong to Oodiscus, 

 but it cannot be determined to which, if any, of the species based 

 on the cephala it should be referred. Compared with the pygidium 

 assigned to O. subgranulatus, it has a more prominent and longer 

 axis. 



Disposition of material. — Figured specimens: U.S.N.M. 146020. 



OODISCUS, species undetermined No. 2 

 Plate 11, figures 12, 13 



Available material. — A few pygidia. 



Description. — The pygidia in question do not appreciably differ 

 in shape from those referred to O. subgranulatus, but lack the 

 ornamentation of the cephala and pygidia of that species. Hence they 

 may belong to a similar species, possibly 0. binodosus, that has a 

 smooth cephalon. The assignment cannot be decided on the basis 

 of the available evidence. 



Occurrence. — Collection cs-4, North Chatham. 



Disposition of material. — Figured specimens: U.S.N.M. 146021. 



Genus SERRODISCUS R. and E. Richter, 1941 

 Type s^toits.—Eodiscus (Serrodiscu^) serratus R. and E. Richter. 



SERRODISCUS SUBCLAVATUS Rasetti, new species 

 Plate 2, figure 1 ; plate 8, figures 10-19 

 Available material— 'Numerous cephala and pygidia, including one 

 cephalon with two thoracic segments attached. 



