CLASSIFICATION OF THE BRACHIOPODA. 87 



septa, and also by the two diverging lines which extend from the extremity of the beak 

 to about two-thirds of the length of the valve, indicating the presence of the large condyle 

 plates and shoe-lifter process.^ Professor Qiienstedt forms for Athyris and Spirigera a 

 small sub-section, which he designates by the name of Terebratula Spiriferina ;" but 

 it seems much more convenient, as well as desirable, to give to each group a distinct 

 appellation, and to place these last in the family SpiriferidcB. 



Geol. range. — This genus seems in our present knowledge restricted to the 

 Palaeozoic era ; appearing first in the Silurian period, it is abundantly distributed in the 

 Devonian age, but until the interior of many doubtful species has been examined, it will 

 not be possible to point out its exact range. 



Examples : A. tumida, Dal. ; Herculea, Barr. ; pseudo-scalprum, Barr. ; Scalprum, 

 Roem. ; plebeia, Ph., sp. ; &c. 



Genus — Spirigera, D'Orb., 1847. 



Type — T. concentrica, Buck., sp. Int., PI. VI, figs. 65 — 70 and 78. 



Athyris and Actinoconchus, 31' Coy (part). 

 Terebratula (part) of the generality of Authors. 

 Spirigera, D'Orhigny. 

 Cleiothyris, King (non Phillips). 

 Retzia ? King. 



Animal unknown, shell inequivalve and variable in shape; circular, subquadrate, 

 elongated, transverse, globose, or depressed, with internal spires; valves articulating by 

 teeth and sockets; beak short, more or less incurved and truncated by a small round 

 aperture lying contiguous to the umbo of the socket valve, or separated by a deltidium 

 in two pieces; no true area; beak-ridges more or less defined; valves convex and divided 

 or not by a mesial fold and sinus ; surface smooth, striated or variously costated, and marked 

 by numerous concentric lines of growth, sometimes produced considerably beyond the 

 margins of the shell in the shape of foliaceous expansions. In the interior of the 

 smaller or dorsal valve, the hinge-plate presents four depressions or pits, which afforded 

 attachment to pedicle muscles; and close to the extremity of the umbo, a small 

 circular aperture, appears at times to communicate with a cylindrical tube^ which, after 



1 Several of the species belonging to this group have been figured and described by M. Barrande, in 

 the 'Ueber die Brachiopoden der Sil. Schichten von Boehmen, 1847.' I am likewise indebted to M. Suess, 

 of Vienna, for much valuable information regarding A. herculea, and for the loan of several of his 

 unpublished figures. 



2 Handbuch der Petrefackunde, p. 4/4, 1851. 



^ The discovery of this remarkable appendage in T. concentrica is entirely due to M. Bouchard, of 

 Boulogne, that distinguished author having many years ago beautifully worked out all the internal 

 characters connected with the type of this genus which abounds in the Devonian Beds of Ferque. The 

 tube has not, however, been hitherto observed in any other species, and therefore we cannot afiirm that 



