NIAGARA GROUP. 



131 



some of them, however, I have been able to detect several vertical lamella, but without any 

 transverse septa. The whole is so minute that these lamellffi may prove to be tubular and not 

 celluliferous. 



The coral presents a variable surface appearance, from the different influences of weathering ; 

 when it has suffered little or nothing from such causes, the entire surface presents a series of 

 stars having a depression in the centre, and apparently confluent at the margins ; where it has 

 been slightly weathered or worn, the stars are limited, and in many cases there is a solid 

 crystalline centre with surrounding rays. A polished transverse section presents the cells with 

 a space between them equal to the diameter of the cell. A vertical section gives the same 

 general appearance. 



This species has not the cells as well defined with the tubular or cellular interstices as the 

 follow'ing, and in this respect does not precisely meet the requirements of the generic character 

 as given by Mr. Dana. It seems, however, to differ too little to require reference to any other 

 genus. 



Fig. 1 a. A portion of the surface, showing the openings of the cells. 



Fig. 1 b. A vertical section produced by weathering. 



Fig. 1 c. Enlargement of 1 a, showing the variable appearance of the cells. 



Fig. 1 d. Enlargement of 1 b, showing the cells as they appear when weathered. 



Fig. 1 c. A magnified view of a polished transverse section. 



Fig. 1 /. A magnified view of a polished vertical section. 



Fig. 1 ^. A magnified view from the lower side of the coral. 



Position and locality. In the lower part of, the Niagara limestone at Lockport. 



instate Collection) 



520. 2. HELIOLITES SPINIPORA («. sp.). 



PL. XXXVI. Fig. 2 a- n. 



Compare Porites tabulata, Loksdale ; Murchison, Sil. System, p. 687, pi. 16, fig. 3. Also 

 fig. 2 o, 6, of Porites piriformis, id. ib. 



Turbinate, pyriform, hemispheric and spheroidal masses, formed of diverging cylindrical 

 tubes with cellular interspaces, often rapidly increasing by interstitial additions of new tubes, 

 and thus becoming spheroidal ; openings of the cells upon the surface circular, with twelve 

 short rays, not confluent ; spaces between the openings cellular ; tubes transversely septate, 

 and externally marked by strong longitudinal striae. A longitudinal section shows cellular in- 

 terspaces, and the interior of the tubes often crowded by spiniform rays nearly meeting in the 

 centre. 



This coral presents such a variety of appearance and character, that it is impossible to give 

 an adequate description in a few words. It occurs mostly in small hemispheric or spheroidal 

 masses, and its great variety of aspect is mainly due to weathering and the effects of different 

 conditions of crystallization of the mass. In many specimens the exterior limits of the cells 

 are not conspicuous, and the stellate openings appear to be confluent or nearly so. In such 



