150 Tlic Life-Hisloni of Sjnrife)' loevis. 



I have mentioned ii number of well characterized species, i. e., 

 forms which taken in their separate geological horizon are dis- 

 tinguishable from other forms in the same horizon. In making 

 a comparative study of them, facts of interest are brought out 

 in regard to each, which may be laid before readers by present- 

 ing them in the form of notes on each of the species. * 



Jt will be noticed, that I use the term species in the restricted 

 modei'n sense, as a morphological species only. Our studies 

 may throw some light on the nature of species in the broader 

 and more theoretical sense. 



SjJirifer crispus, Hisinger (not of Linn.), (Vet. Akad. Haiis- 

 lingen, tab. VII, fig. 4, 1826, figured by J3avidson in Bi'it, Sil. 

 Brach., pi. X, figs. 13 — 15), with the associated forms, is ap- 

 j)arently the earliest type of S. fimhriatus and setigerus, etc., 

 of later times in America, and of forms under other names in 

 Great Britain, Europe and elsewliere. 



■ This species is described by Hall as Delihyrls daminea, in 

 Geol. Rept. of 4th Dist. N. Y., pp. 105, 106, and figured, 1. c, 

 tig. 3, and later it was more fully described and figured, and 

 referred to S. crupuH, in Vol. 2 of Pal. of N. Y., p. 262, fig. 3, 

 i-k, of PI. LIV. Whether or not this form, with its closely re- 

 lated ones, is identical __wit]i those of the upper Llandovery beds, 

 and up to the Ludlow formations in Great Britain, called Spiri- 

 fer crispus, His., by Davidson, and ^S*. elevahis, Dalman, of the 

 upper Llandovery, these are Avithout doubt the representatives 

 on this side the Atlantic of the Eu]-opean spirifers included un- 

 der the siDCcific names elevatns, Dalman, — crispus, His., and 

 — svlcatus, His., and present like variation and like similarity, 

 and also were Avidely distributed and abundant. 



The following are the main peculiarities of the species as 



* Further study lias showii that the genus Spirifer began and continued 

 in about four well-marked kinds, i. e., types, with the variations of each. 



The three principal types are radialus, crispus, and sulcatus, — and I am 

 inclined to regard Cyrtia exporrecia, Wahl. as the central tjqae of the fourth 

 kind. 



The corniferous species Spirifer muia of Billings, although at first glance 

 appearing to belong to the S. crispus kind, I think (I have not seen good 

 specimens) is a representative of the S. radialus combination of specific 

 characters. . 



