NIAGARA LIMESTONE OF CHICAGO, ILLINOIS. 



83 



GEOGRAPHICAL DISTRIBUTION OF NIAGARA SPECIES IDENTIFIED AT CHICAGO. 



ENUMERATION OF SPECIES. 



Petraia calicula Hall sp., Pal. N. Y., ii. p. Ill, pi. xxxii. fig. 1, a-Jc. 



Zaphrentis turbinatus Hall sp., Pal. N. Y., ii. p. 112, pi. xxxii. fig. 2. 



Cysiipliyllum sp ? A fragment generically well marked. 



Diphyphyllum ccespitosiim Hall sp., Pal. N. Y., ii. p. 116, pi. xxxiii. fig. 1, a-b. 



Favosites gothlandica Lam. (F. niagarensis Hall.) We adopt the suggestion of Billings 

 (Canad. Journal, March, 1859, p. 99), in referring this form back to the original species. It 

 occurs abundantly in the upper part of the quarry. 



Favosites venustus ? Hall sp., Pal. N. Y., ii. p. 120, pi. xxxiv. fig. 1, a - i. 



The agreement is not striking. This is an expanded, incrusting coral, adapting itself to 

 the inequalities of the underlying surface, and, in places, developing tubercular masses. 

 The tubes are ordinarily not more than an eighth of an inch long, but, in the tubercles 

 become sometimes half an inch in length. In the tuberculous parts, the diaphragms are 

 seen to be direct and crowded. No indications of a radial system are seen. The cell- 

 mouths are conformable to this species. The Chicago fossil bears considerable resemblance 

 to Thecostcgites hemisphcericus Rom. (Sil. Fauna des Westl. Tenn. Taf. ii. fig. 3). 



* These species are not enumerated by Hall among the fossils of Wisconsin. 



