510 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



Syeingopoea sueculaeia n. sp. 

 PL LXVII, figs. 4«, 46. 



Similar to the above, but larger. Average diameter of individual 

 corallites, 2.5 mm. Walls thickened by stereoplasma. Infundibuliform 

 dissepimental tissue well developed, spinulose; the spines appear as nodes 

 of greater or less prolongation, often radially directed between parallel 

 dissepiments. They are irregular, however, have no constant connection 

 with the spiniform septa, and never give the corallite the septate appearance 

 of rugose corals. 



This species is, in a general way, very close to the preceding, but the 

 eye differentiates them at a glance on the basis of size. The walls of 8. sur- 

 cularia are more thickened by stereoplasma than are those of S. aculeata, 

 and the septal spines, which are embedded in it, appear to be relatively not 

 so long, so numerous, nor in so many rows. 



Both species are easily distinguished from 8. multattenuata McChes., by 

 the fact that the corallites in the latter often grow in contact and are 

 scantily supplied with septal spines. 



Formation and locality: Madison limestone, White Mountain, Absaroka 

 Range; Upper Gallatin Valley, west of Bighorn Pass; Arnold Hague. 

 Crowfoot Ridge, Gallatin Range, bed 28; J. P. Iddings and W. H. Weed. 

 Head of Gallatin River, west of Three River Peak; Arnold Hague. 



MICHELINIA DeKoninck, 1842. 



MlCHELINIA PLACENTA White. 

 PL LXVII, tigs. 3a, 3b. 

 Miclielinia (?) placenta White, 1SS3: Twelfth Aim. Rept. U. S. Geol. G-eogr. Surv. 

 Terr., Pt. I, p. 157, IT. XXXIX, tigs. la-Id. 



This species is known at two localities in the Yellowstone National Park. 

 It appears to be the same form described by White, from Sedalia, Missouri, 

 where it occurs at the top of the Chouteau limestone. I have not seen 

 specimens from White's locality, but his description and figures show the 

 two forms to be very similar. 



Formation and locality: Madison limestone, east side of Gallatin 

 River west of Electric Peak; divide between Gallatin Valley and Panther 

 Creek, near Bighorn Pass, Gallatin Range, bed 24; Arnold Hague. Top of 

 the Chouteau limestone, Sedalia, Missouri. 



