SPIRIFERINA. 47 



concentric laminae of growth. Shell-structure perforated by large canals. Proportions 

 variable ; two Devonian specimens have measured : 



Length 8, width 11 lines. 



Obs. The question relating to the origin and recurrence of the Spiriferina we are at 

 present describing is one of some difficulty, demanding considerable attention and further 

 research. It is an exceedingly variable shell, being small (adult) in some localities or 

 strata, while in others it has attained considerably larger dimensions. Thus, at Looe, in 

 Cornwall, the shell is large, while at Partington it is apparently always of small size. It 

 is my strong impression that we must look for its first appearance or origin in the Silurian 

 time, and that it continued to be represented, with some slight modifications, in the 

 Devonian, Carboniferous, Permian, and perhaps up to the Jurassic period (?). One thing 

 certain is, that, having compared some of our Scottish Carboniferous specimens, for example, 

 with the Silurian Anomia crispa of Linnaeus, 1 I could detect hardly any modification in 

 shape or character. Other examples strongly resemble Delthyris sulcata, Hisinger. as 

 well as some other so-termed closely related American forms. I will not, however, at 

 present, go further into the question, but content myself by stating that our British 

 Devonian specimens appear to be specifically the same as those we find so abundantly in 

 the Carboniferous and Permian periods, and to which Schlotheim has applied the denomi- 

 nation of cristata, and Sowerby that of odoplicata. At Looe distorted internal casts are 

 abundant ; and it occurs in company with Uncites gryphus in the Dartington dolomitic 

 limestone of the Middle Devonian time. Some specimens have also been found in the 

 Pilton and Marwood beds. As we have already had occasion to observe, it is difficult 

 to obtain from the Palaeozoic limestones specimens with their outer surface perfectly pre- 

 served, and it is usually from soft shales that we must seek for examples preserving their 

 outer sculpture ; this is why the concentric laminae which cover the surface of the shell, 

 and which sometimes overlap each other in perfectly preserved specimens of Sp. cristata, 

 and its Carboniferous and Devonian representatives, are not commonly seen ; this, in 

 addition to the variability in the number of ribs, has led to the fabrication of several so- 

 termed species. Sp. aculeatus, Schnur, appears also to be very closely related to the shell 

 under description. 



1 This is not the place, however, to enter more deeply into the question relating to the Silurian form. 

 In his ' Ipsa Linnsci Conchylia,' by S. Hanley, 1855, we find at p. 128 the following statement : — "I cannot 

 find a specimen in the Linnsean Cabinet to which the whole of the description will apply. The Swedes 

 (Wahlenberg, Nilsson, Hisinger) have handed down so many of the fossil species of our author in an un- 

 broken chain of tradition, confirmed in so many cases by the types in the collection of Linnaeus, that the 

 Spirifer recognized by them (Terebrat. crispa, Hising., 'Vet. Acad. Handl.,' 1828, pi. vii, fig. 4 ; Delthyris 

 crispa, Dalman, 'Vet. Acad. Handl.,' 1827, pi. iii, fig. 6; Hisinger, * Lethsea Suecica,' pi. xxiv, fig. 5) for 

 this species of Anomia may be accepted as such with some degree of confidence. (Sharpe, MS.) This 

 opinion is in harmony with that of Mr. Davidson ;" but the subject will be fully discussed iu our mono- 

 graph of Silurian species. 



