NIAGARA GROUP. 



123 



513. 3. ASTROCERIUM PYRIFORME (n. sp.). 



PL. XXXIV A. Fig. la- e. 



Irregularly subturbinate, pyriform or spheroidal ; cells angular, radiating from a more or 

 less extended base, often from a narrow area, spreading out above and rapidly increasing by 

 the addition of interstitial tubes ; tubes opening upon the surface by well defined angular 

 mouths, which are seen of all sizes and forms, from triangular to hexagonal, in their different 

 stages of development ; cells within divided by transverse septa, and one or more rows of fine 

 spiniform rays between each pair of septa. 



This species presents but slight differences from the last, and may perhaps be only a variety 

 of the same. The most obvious difference appears in the openings of the cells upon the surface, 

 which are usually smaller than in the preceding species, more uniformly angular, and do not 

 present the larger nearly round openings which occur at intervals in the last species. It is often 

 difficult, from any external character, to discover any distinction between this fossil and some 

 species of Favosites ; but a careful examination of the internal structure has shown, in nearly 

 all instances, the peculiar stellate structure and spiniform rays. 



Fig. 1 a. A spheroidal form of this species. 



Fig. 1 6. A turbinate form, the cells increasing rapidly from a narrow base. 



Fig. 1 c. An irregular turbinate form of larger size. 



Fig. I d. A portion enlarged, showing the internal structure of the cells. 



In this individual both the septa and rays are nearly obliterated, but enough re- 

 mains to decide the generic characters of the species. 



Fig. 1 e. An enlarged portion from the inner walls of the cells, showing the granulated or pa- 

 pillose surface from the bases of the spiniform rays. 



The specimens figured above are nearly solid throughout, the cells being filled to the openings, 

 so that the stellate structure is very obscure, though evidently existing in all the specimens 

 figured. 



Position and locality. This species occurs in the shale of the group at Rochester, Wolcott 

 and Lockport, and more rarely in the limestone at Rochester and Lockport. (State Collection.) 



514. 4. ASTROCERIUM CONSTRICTUxM (n. sp.). 



PL. XXXI V A. Figs. 2 o-c, and3«-e. 



Massive, hemispheric ; cells minutely stellate ; coral dividing into columns, which appear 

 as if constricted at intervals. 



This species has the columns a little larger than Chatetes lycoperdon, and more strongly 

 constricted at intervals. These characters alone are sufl[icient to distinguish it on careful com- 

 parison, though from a cursory examination it would easily be mistaken for that one. When 

 the ends of the cells are visible, however, there is no difficulty in distinguishing the true cha- 



