144 Tho Lifc-lIiKlonj of Spirifcr hen's. 



most thorouglily developed specimens. We will refer later to 

 other interesting facts in this connection, only mentioning 

 now that wherever these traces of plications are found, they appear 

 on the marginal port ioNs of the shell, and never high up toward 

 the beak. 



There is still another character which is highly important, 

 and it forms one of the most valnable criteria in tracing out the 

 relations of the species. Hall, evidently, had not observed it, 

 and I can find no printed evidence that any author has hereto- 

 fore noted tlie fact next described.* 



Concentric series of minute radiatijig lines. — The surfaces of 

 specimens well developed, and which did not suffer from attrition 

 before being safely covered np, show under a glass of moderate 

 magnifying power, fine concentric rows of short radiating lines, 

 such as are seen coarse and strong in Spirifer finibriatus of the 

 Hamilton and Corniferous, and in several other species of other 

 periods, and which furnished Davidson the distinguishing char- 

 acter by which to separate the Devonian S. curvatus, Schl. from 

 the Carboniferous S. glaher, Martin. It is surprising that Hall 

 did not notice this fact when the strong resemblance to the Brit- 

 ish representatives of >S'. glaher, Martin, figured by Davidson, 

 was specially mentioned by him. 



Further comment will be made upon these points. 



<r 



We have drawn attention to the few characteristic marks of 

 this species: — To enumerate them, they are evident, as follows, 



a. 1st, in the form and proportions of the shells; 



}). 2nd, in the size; 



c. 3d, in the prominence and over-arching of the beak; 



d. 4th, in the short and high cardinal area; 



e. 5th, in the triangular aperture covered by arched pseudo- 

 del tidium; 



/. 6th, in the smoothness of the surface; 



g. 7th, in the concentric series of minute radiating lines; 



* Since this paper was completed, and an abstract published, I learned that Prof. Hall 

 had previously observed the surface markings of Sp. Icevis referred to, and had already pre- 

 pared plates illustrating the fact, for a work which is as yet unpublished. 



Mat, 1881. H. S. W. 



