184 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. '64 



the species now referred to the genus, but this character is not 

 distinct in A. lahrosum (pi. 25, fig. 5), A. linnarssoni (pi. 25, figs. 

 7, ya), and A. ? prospectense (pi. 25, fig. 8).' This may be owing 

 partly to the conditions of preservation of the cranidia, as the asso- 

 ciated free cheek of A. linnarssoni (pi. 25, fig. ya) indicates a frontal 

 rim not unlike that of A. suhcoronaUim (pi. 25, fig. 2). 



As far as known to me, the outer surface of the test is smooth to 

 the unaided eye and minutely roughened and apparently pitted or 

 porous when examined with a strong lens. 



ALOKISTOCARE ALTHEA, new species 



Plate 25, figs. 3, 2,a, 4, 4a 



This species is represented by casts of several specimens of the 

 cranidium that are preserved in a fine sandstone matrix. Nothing 

 is known of the surface of the test, and only indistinct traces of the 

 glabellar furrows are to be seen. The most nearly related cranidium 

 is that represented by figures 4, 4a, plate 25, which differs in details of 

 frontal rim and boss. The two forms are, however, closely related 

 and may belong to the same species, the apparent differences being 

 caused by the condition of preservation of the specimens. Alokis- 

 tocare althea occurs in a fine sandstone matrix, and the variety in a 

 sandy shale ; the two beds are separated stratigraphically by-^ 200 to 

 300 feet in thickness of sandy shale. 



The specimens preserving the thorax (figs. 4, 4a) are from the 

 Bright Angel shale, and the cranidia represented by figures 3 and 3a 

 I collected in 1882 in the upper part of the Tapeats sandstone, about 

 200 feet below the horizon in the shale. The latter are casts pre- 

 served in a fine sandstone matrix. 



Formation and locality. — Middle Cambrian: (74) Tapeats sand- 

 stone; at the head of Nunkoweap Valley, Grand Canyon of the 

 Colorado River; and 



Middle Cambrian: (746) Bright Angel shale 100 feet (30.4 m.) 

 above Tapeats sandstone; on west side of Cameron trail about 0.5 

 mile (0.8 km.) north of Indian Garden spring; south side Grand 

 Canyon of the Colorado River, both from Coconino County, Arizona. 



Collected and presented by Niles J. Cameron, 191 1. 



ALOKISTOCARE ? LABROSUM, new species 



Plate 25, figs. 5, sa 

 This species is represented by numerous specimens of the cra- 

 nidium that have very strongly marked characters which serve to 



