CAEBONI FERGUS PERIOD. 103 



prominent solid axis of that species, separating so readily from the smTound- 

 ing parts in broken specimens, caused it for a time to be referred to the genus 

 Cyatliaxonia, but Mr. Meek has shown (loc. cit.) that it has the internal structure 

 of Lopliopliyllum. 



Position and locality. — Strata of the Carboniferous period ; near Santa 

 Fe, New Mexico, and at Rock Creek, Lake County, Colorado. 



Genus LITHOSTROTION Fleming, 1828 



Lithostrotion Whitneyi Meek. 



Plate VI, fig. 1 a, b, and c. 



Lithostrotion Whitneyi Meek, 1875, Pal. of U. S. Geol. Expl. 40th Parallel, (manuscript). 



Corallum fasciculated ; coi"alHtes cylindrical, somewhat flexuous and 

 irregular, generally separate but seldom distant, and sometimes in contact ; 

 epitheca thin but distinct, marked by wrinkles and encircling lines of 

 growth ; columella small and very narrow, being laterally compressed ; 

 pi-incipal rays from twenty to twenty-eight in number, according to the 

 size of the polypite, alternating with smaller rays ; tabulae numerous, com- 

 paratively broad, transverse or arching downward from the columella ; 

 vesicular zone nan-ow, composed of from three to five layers of vesicles. 



Diameter of polypites, from eight to fourteen millimeters. 



In splitting and polishing a polypite, so as to obtain a view of the 

 internal structure, it is often difficult to make the section in such a manner 

 as to show the columella, because it is so small and narrow. If the section 

 is made parallel with one of its flat sides, but not cutting through it, the 

 tabulae appear to be separate from each other in all parts, and to extend 

 directly across the polypite, as in Gyatliophyllmn. Such a section is 

 shown in figure 1 c, Plate VI. If the section passes obliquely through the 

 columella, its character is indistinctly shown, as in figure 1 & of the same 

 plate. The section given by Mr. Meek in his illustrations of the species is 

 through the short diameter of the columella. 



Position and locality. — Strata of the Carboniferous period ; Fossil Hill 

 and Ice Creek, Steptoe Valley, White Pine Comity, Nevada. 



