508 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



PORIFERA. 



HOLASTERELLA Carter, 1852. 



HoLASTERELLA WBIGHTI var. AMERICANA 11. vai\ 

 PI. LXXI, fig. 11«. 



The only trace of sponge remains which has been observed in Yellow- 

 stone National Park consists of two or three delicate silicified spicules, 

 which, for lack of a better designation, I have called by the above name. 

 While closely related to Garter's species, 1 I think it is undoubtedly distinct. 

 At the same time, in view of the limited amount of material at my disposal, 

 I do not feel justified in proposing a new specific name, while the occurrence 

 of the form seemed worthy of notice and a name of some sort desirable. 



The spicules in question are of the regular hexactinellid type. The 

 six arms are stout and short, each quickly subdividing into four long 

 tapering branches. These are set at an acute angle with one another, and 

 ornamented with fine nodes, which tend to an arrangement in transverse 

 rows, giving the branches a finely annulated appearance. 



The genus Holasterella, so far as I am aware, is restricted in its range 

 to Lower Carboniferous strata; and this is the first notice of its occurrence 

 in this country. 



Formation and locality: Madison limestone, divide between Gallatin 

 Valley and Panther Creek, near Bighorn Pass, Gallatin Range, bed 24; 

 Arnold Hague. 



C(ELENTERATA. 



AULOPORA Goldfuss, 1826. 



AULOPORA GEOMETRICA 11. Sp. 

 PI. LXVII, fig. Crt, 



Corallum free (?), spreading. Corallites small, each regularly budding 

 off two other individuals, which diverge at an angle of about 120°, so that 

 the colony as a whole presents a regular network with hexagonal openings. 

 Length of corallites about 5 mm.; diameter, from 1.25 to 1.5 mm 



■ See Carter, 1880: Ami. Mag. Nat. Hist., Vol. VI, p. 209.. t. 14b, figs. 1-17; and Hiude, 1883: Cat. 

 Foss. Sponges, Brit. Mua., p. 153, PI. XXXII, figs. i-ig. 



