CLASSIFICATION OF THE BRACHIOPODA. 115 



the Devonian period, attaining its specific maximum during the Carboniferous epoch, 

 above which no authenticated example has been yet recorded. 



Examples: C. striatella, sp., Dalman. ; comoides, J. Sow.; concentrica, De Kon. ; 

 papilionacea, Phil. ; Dalmaniana, De Kon. ; sulcata, M'Coy ; variolata, D'Orb. ; armata, 

 Bouch. ; convoluta, Phil. ; Ferneuili, Bar. ; Bucldana, De Kon. j &c. 



Genus — Strophalosia, King, 1844. 



rype— S. EXCAVATA, Geinits, sp. Int., PI. VIII, figs. 203—211. 



Spondylus (Golbfussi), MUnster, 1839. 



Orthis (excavata), Geinits, 1842. 



Strophalosia (=LeptvENalosia), King, 1844; M'Coy, &c. 



Productus, Be Verneuil, De Koninck, and the generality of Authors. 



Orthothrix, Geinitz, 1848. 



Shell variable in shape, more or less circular, transverse or elongated, larger or dental 

 valve convex, smaller one concave and following the curves of the other ; surface 

 ornamented by scattered tubular spines ; beak often irregular, having been affixed by its 

 substance to submarine objects ; a small well-defined area in both valves, divided by a 

 pseudo-deltidium : hinge-line straight ; valves articulated by teeth and sockets, the 

 former situated on each side of the base of the deltidium of the larger valve, and the 

 latter on both sides of a cardinal muscular process of the socket valve. Internally, 

 a longitudinal raised ridge extends from the cardinal process to about half the length of 

 the valve, on either side of which is seen a small ovate raised muscular scar : the reniform 

 impressions are rather large, their prominent outer edges issue from between the adductor 

 scars, gradually arch forwards and outwards on each side, then turning backwards for 

 about half their length, and finally run inwards horizontally to meet each other near the 

 extremity of the mesial septum. 



Obs. In 1844, Professor King proposed to separate from Productus certain shells 

 possessing a well developed condyloid hinge, area, and deltidium, to which he applied 

 the term Strophalosia.^ This view has been sanctioned by some, but rejected by 

 others who did not consider the distinctive characters sufficient to warrant the establish- 

 ment of another genus.^ About two or more years after the publication of Professor 

 King's views. Dr. Geinitz proposed the generic appellation Orthothrix^ for the same 

 shells already known by that of Strophalosia. For a long time, I agreed with my 

 friend M. de Koninck in resisting the establishment of this section, but after minute 

 comparisons of the shells in question, aided by the kind assistance of Professor King, I 

 must admit the existence of some grounds for establishing a separate group or sub- 



1 See Annals and Mag. of Nat. Hist., vol. xviii, p. 92, 1846 ; and Mon. of English Per. Foss., 1849. 



2 See De Koninck; Monographic des Genres Productus et Chonetes, p. 10, 1847. 

 * Die Vers, der Zechsteingebirges, &c., Dresden, 1848. 



