402 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



The thorax has 14 segments, and the pygidium fovir and a terminal 

 section on the axis. There are usually three pairs of border spines, 

 but in one specimen there are four pairs (see pi. 65, fig. 4a). On 

 the under side the base of the spines merges into the doublure (fig. 

 4^). The pygidium of M. callas has only one pair of border spines 

 at its antero-lateral angle. These resemble closely the border spines 

 of Corynexochus {Bonnia) parvulus. The variation in the number 

 of border spines is not necessarily of generic value, and it may be 

 in some instances of less than specific value. 



Surface marked by fine, shallow pits. 



The largest entire specimen of the dorsal shield of Marjuinia typa 

 has a length of 73 mm. 



Genotype. — Marpimia typa Walcott. 



The stratigraphic range is limited to the Marjum formation. 

 Marjumia typa occurs about 250 feet (76 m.) and 575 feet (176 m.) 

 below M. callas. As far as now known, species of the genus occur 

 only in the House Range of western Utah. 



MARJUMIA CALLAS, new species 



Plate 65, figs. 3, 3a-b 



This species is represented by specimens of the cranidium, free 

 cheeks and pygidium. The cranidium and free cheeks are^much like 

 those parts in Marjumia typa except that the side furrows of the 

 glabella are very faint in M. callas. The pygidium differs from that 

 of M.Jypa in having but one marginal spine on each side and a 

 shorter axis. The border spine appears to be a continuation of the 

 anterior anchylosed segment that is merged into the border where 

 it crosses and extends outward beyond it. 



Surface of cranidium and pygidium marked by very fine shallow 

 pittings. The largest cranidium has a length of 17 mm. 



Formation and locality. — Middle Cambrian: (sir) Marjum for- 

 mation; gray limestone forming lower portion of la of the section in 

 cHff facing northeast, i mile (1.6 km.) southeast of Marjum Pass, 

 House Range, Millard County, Utah. 



MARIUMIA TYPA Walcott 



Plate 65, figs. 4, 4a-b 



Owenella typa Walcott, 1908, Smithsonian Misc. Coll.. Vol. 53, p. 180 

 (Name listed under ic, id. Ozvenella was preoccupied.) 



The principal characters of this species are outlined in the remark*, 

 on the genus Marjumia. The species is quite abundant in dark-gray, 



