part 2] 



8YRI2\~G0THYJRIS AND SPIIiIFEEIJS T A. 



211 



Spiriferina, until more evidence as to their internal structures is 

 available. 



The Carboniferous ' Spiriferinas ' of North America also comprise- 

 two similar groups. The first type is there represented by Sp. ken- 

 tuckyeusis, in which the plications are small, numerous, and crossed 

 by closely-packed concentric lamelhe ; while the second is represented 

 by forms like Sp. spiuosa, which strongly resembles the British 

 Sp. octoftlimta. 1 According to J. Hall & J. M. Clarke, the jugum 

 of Sp. kentuckyensis differs from that of the Liassic Sp. rostrate 



Fig. 5. — Form of the anterior margin of the valves of 

 Spiriferina and associated genera. 



a = Spiriferina insculpta, Carboniferous Limestone (D). 



b = Spiriferina octoplicata, Carboniferous Limestone (D). 



c = Spiriferina perplicata. Carboniferous Limestone (D). 



d — Spiriferina cristata, Permian. 



e =— Spiriferina iralcotti, Lower Lias. 



f -- Punctospirifer scabricosta mut. redesdalensis, Carboniferous 



Limestone (D). 

 g =£ Punctospirifer scabricosta mut. ashfellensis, Carboniferous] 



Limestone (S). 

 h= Spiriferina multiplicata, Permian; 

 i = Spiriferina oxygona, Lower Lias. 



in that its lateral portions converge upwards between the primary 

 lamella' of the spires, and form a structure resembling an inverted 

 V, in stead of being a simple transverse loop as in the latter species. 2 

 This fact favours the separation here suggested, especially as the 

 jngnni of Punctospirifer is of a similar nature ; while, in a speci- 

 men of Sp. cristata figured by H. B. Geinitz, 3 the jugum was like 

 that of Sp. rostrafa. 



The Carboniferous shells are considerably smaller than those 



1 See Girty [9] pp. 371- 72. 2 Hall & Clarke [14] p. 54. 



3 ' Dyas oder Zechsteinformation & das Botblieg-ende ' 1861, pi. xvi, fig. 2. 



