148 Tlic Life-IIhturji of Sjiirifer hevis. 



It is a rather rare cliaracter among the species of Spirifer, 

 and becomes a valuable mark in tracing relationship. * 



The species Sinrlfer fimhriattis. Con., is seen to be a variable? 

 species of wide range. It is traced down as far as the Oriskany, 

 and as Prof. Hall suggests, we may recognize related forms in 

 8. pseudoUneatus and 8. setigerus of the Carboniferous ; but in 

 its so-called specific characters, it is the first of its type. In 

 geographical range, it is recorded from New York, — throughout 

 the State, — Canada West, Ohio, in the Mississippi Valley, and in 

 Vi rginia. f 



As a specific form, it seems to have reached its perfection in 

 the Hamilton. 



The comparison we have made between the two species 8piri- 

 fer loevis, Hall, and ;iS'. fimhriatus, Conrad, appears to leave 

 little doubt that the former is, strictly speaking, a descendent 

 of the latter; and tlie tracing of the marks of relationship brings 

 the latter into line with a series of forms reaching back to tlio 

 Niagara Period and forward at least to the upper part of the 

 Carboniferous age. 



A study of the series of related forms has brought out many 

 facts which may be interesting to students of Palasontology, and 

 to some whose studies may cover a wider field ; and in the fol- 

 lowing pages I will attempt to give in orderly manner the results 

 of my researches. 



A number of species have been considered, but those in which 

 the marks of relationship appear most distinctly are the fol- 

 lowing : — 



In the Niagai'a period, are — 



82nrifer hicostatus, Vanuxom, ^S'. crispus, Ilisinger, and ;S'. 

 aulcatus, His. 



* See Plate XXXIV, Fig. 9, Suppl. to Brit. Periinan Bracliiopoda, Pa- 

 laeontological Soc. Publications, and Davidson's descriptions of the concen- 

 tric roAvs of spines of <S. Uneatus, p. 375, 1. c. 



These tubular spines with double perforation I have detected for the first 

 time in any American Spirifer, in a si^ecimen of i,?) Sp. fimhriaius (a frag- 

 ment from the base of Chemung group). 



f I have found fragmental specimens of clearly marked Sp. fimhriaius 

 near the base of the Chemung, with the concentric rows of surface-markings, 

 and with about the normal number of plications of surface. 



