40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



These are all represented by small, evidently immature specimens. 

 No fragments of either cephala or thoracic segments seem to indicate 

 the presence of animals much larger than the cephala illustrated. 



Genus PAEDEUMIAS Walcott, 1910 

 Type species. — Paedeumias transitans Walcott. 



PAEDEUMIAS, species undetermined No. 1 



Plate 12, figures 23-25 



Available material. — Fairly numerous, complete cephala from 1.5 

 to 4 mm in length. 



Description. — Glabella well-defined, narrow, parallel-sided, with 

 frontal lobe not wider than the posterior lobes. Frontal lobe ovate, 

 defined by a furrow deep at the sides, shallow but distinct medially. 

 Next three lobes of about equal length, separated by deep, trans- 

 verse furrows at the sides, not extended medially. Occipital furrow 

 similar to the preceding glabellar furrows; occipital ring apparently 

 extended into a short spine, not well preserved in any of the cephala. 

 Palpebral lobes separated by a shallow depression from frontal gla- 

 bellar lobe, with curvature increasing backward, almost reaching the 

 posterior cephalic margin. There is a fairly wide, well-defined space 

 between the glabella and the palpebral lobe. Border wide, convex, 

 of about the same width frontally and laterally. Distance from ante- 

 rior end of glabella to anterior border furrow almost equal to length 

 of frontal glabellar lobe. A median ridge connecting the front end 

 of the glabella with the border furrow is visible at least in the larger 

 specimens. From the posterior end of the palpebral lobe a narrow 

 outward-directed ridge reaches the posterior cephalic margin at the 

 base of a moderately long intergenal spine. Beyond this spine, the 

 posterior margin turns slightly forward to the base of the genal spine, 

 which is less conspicuous than the intergenal spine. 



The preceding description was based on cephala about 4 mm in 

 length. In a fairly well-preserved cephalon 1.5 mm in length illus- 

 trated herein, the intergenal spines are very close to the genal angle ; 

 in addition, there is a pair of small procranidial spines. These changes 

 in the relative size and position of the spines, as far as can be ascer- 

 tained from the meager material available, seem to parallel those 

 observed by Palmer (1957) in the ontogeny of Olenellus gilberti. 



Occurrence. — Collection cs-4. North Chatham. 



