CAMBRIAN FOSSILS. 447 



Dicellomus nanus M. and H. sp. 

 PI. LX, figs. 3, 3a-d. 



Obolella nana Meek and Hayden, 1861 : Proc. Acad. Nat. Sci. Philadelphia, 2d series, 

 Vol. V, p. 435. Billings, 1S62: Paleozoic Fossils, Vol. I, p. 07. Hayden, 1863: 

 Am. Jour. Sci., 2d series, Vol. XXXIII, p. 73. Meek and Hayden, 1864: Pal. 

 Upper Missouri, Pt. I, p. 4, PI. I, figs. 3a-d. Whitfield, 1880 : U. S. Geog. and 

 Geol. Surv. Eocky Mountain Region, p. 340, PI. II, figs. 14-17. Hall and Clarke, 

 1892: Pal. New York, Vol. VIII, Pt. I, p. 69. 



Only a single specimen of the outer surface of a ventral valve of this 

 species occurs in the collection. It has the characteristic appearance of 

 the species. The species also occurs in abundance in the Little Rocky 

 Mountains to the north, in Montana, and also to the eastward in the Black 

 Hills. 



The specimen from the Park is illustrated, and, in addition, the types 

 from the Black Hills and two specimens from the Little Rocky Mountains. 



Formation and locality: Upper Cambrian, Gallatin limestone (upper 

 portion); Crowfoot section, Gallatin Range, Yellowstone National Park. 



IPHIDEA Billings. 



Iphidea sctjlptilis Meek. 



PI. LX, figs. 5, 5a-c. 



Iphidea (?!) sculptilis Meek, 1873: Sixth Ann. Kept. U. S. Geol. and Geog. Surv. Terr., 



for the year 1872, p. 479. 

 Eutorgina minutissima Hall and Whitfield, 1877: U. S. Geol. Expl. 40th Par., Vol. IV, 



p. 207, PL I, figs. 11, 12. 

 Eutorgina sculptilis Walcott, 1884: Mon. IT. S. Geol. Surv., Vol. VIII, p. 20, PI. I, figs. 



7, la-b; PL IX, fig. 7. 



In the description of Iphidea (!*?) scittytilis, Mr. Meek decided that, as 

 the shell had a very narrow, slightly flattened margin on each side, repre- 

 senting a false area, and as there seemed to be a wide, open, triangular 

 foramen, it could not be referred to the genus Acrotreta or the genus 

 Iphidea. He was not positive that there was not a permanent pseudo- 

 deltidium present, but, assuming the absence of that structure, and with the 

 probability that when all the characters of the shell were known it would 

 be found to belong to a different genus, either of the Brachiopoda or of 

 some other group, he would propose for the genus the name " Micromitra." 



