EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 49 



specimen the zones with distant tabulae have been removed, leaving gal- 

 leries of the parts which have been made more compact by the abundant 

 squamulae. The pores are mostly arranged in two rows on the sides of the 

 corallites and provided with raised margins. 



Favosites hemisphaericus is a widespread Onondaga lime- 

 stone species. 



Rominger op. cit. [p. 20] has stated that Siluric Favosites differ from the 

 Devonic species by invariably having single diaphragms, and by the spinular 

 character of the radial crests, the Devonic forms having squamulae instead 

 of spinules. This statement is corroborated by Lambe. In the Dalhousie 

 fauna, however, we have these two types commingled ; the form with the 

 complete tabulae and septal spines (F . h e 1 d e r b e r g i a e) is by far the 

 rarer of the two and the form with the Devonic characters is the one prevail- 

 ing. This fact demonstrates that mingling of the two groups of species of 

 Favosites is possible around the boundary of the Siluric and Devonic. 



Horizon. Nos. i, 10, 16. 



Favosites helderbergiae Hall 



See pt i, p. 218 



Favosites helderbergiae Hall. N. Y. State Mus. Rep't 26. 1874. p.m 



Among the very abundant specimens of Favosites at this locality two 

 types can be microscopically distinguished by the size of the corallites. 

 That with the larger corallites may be readily assigned .to the F. n iaga- 

 rensis-helderbergiae group. Mr Lambe has identified specimens 

 from Dalhousie as F . n i a g a r e n s i s , stating that the difference between 

 the latter and F. helderbergiae, as cited in Palaeontology of New 

 York, volume 6, does not hold true and that the only difference between the 

 two forms, which are unlike in the size of the corallites, character of spini- 

 form septa and tabulae, appears to be in the shape of the coralla, which in 

 F. niagarensis are spherical or clavate, and in the other species lenticu- 

 lar, depressed, rounded or hemispherical. The former is also said to have had 

 a small basal attachment. Application of these criteria and a comparison of 

 the Dalhousie specimens with our large series of sections of F . niagaren- 

 sis and with the type of F. helderbergiae in the New York State 

 collections have corroborated Mr Lambe's conclusions only in a general way. 



It actually appears that only a few of the specimens, viz, those with the 

 largest corallites (from 2 to 2.5 mm in diameter) have the internal structure 

 of this niagarensis-helderbergiae group ; all the others have a very different 

 structure. The former and fewer are partly club-shaped and in part broadly 

 expanded and would not furnish any specific character in their shape. In 

 sections, further, the septal spines are not nearly so frequent as in typical 

 F. niagarensis and are also noticeably smaller, so that they are difficult 



