CLASSIFICATION OF THE BRACHIOPODA. 99 



they are produced in the form of free, long, and narrow lamellae, to which the cirrated 

 arms were of course attached. The exact position and form of the different muscles has 

 not been yet completely made out ; but in some species the quadruple impressions of 

 the adductor are clearly defined. 



Geol. range. — The genus first appeared in the lower Silurian epoch, and continued, 

 uninterruptedly, to the carboniferous period, above which no authenticated example has 

 been yet discovered. 



Examples : F. Knightii, Sow. ; conchidium, Linn., sp. ; borealis, Eichw., sp. ; galeatus, 

 Dal., sp. ; Vogidicus, Vern. ; llngiiiferus, Sow. ; Sieberi, Barr. ; oblongus, Sow. ; oblatus' 

 Barr. ; pelagicus, Barr. ; caducus, Barr. ; &c. 



Sub-Family? PORAMBONITID^. 



Animal unknown, but evidently attached, at least during a portion of its existence, by 

 a muscular pedicle ; no calcified process for the support of the oral appendages, which 

 were probably fleshy and spirally coiled. In the interior of each valve two diverging septa 

 originate from within the beaks ; structure fibrous and impunctate. 



Obs. As so little is known of the internal organisation of the curious shells composing 

 the genus Porambonites, I have not ventured to follow M. d'Orbigny and Prof. King, in 

 placing it in the family Rhgnchonellida ; but preferred, for the present, to leave it by 

 itself in a small sub-family. Its place is, however, I believe between the Bhg?icho7iellida 

 and Strophomenida. 



Genus — Porambonites, Pander, 1830.^ 



Type—?. ^auiRosTius, Schl, sp. Int., PI. VII, figs. 120—126. 



Teuebratulites (/EQUIROSTRIS), Schl. 



Terebratula (part), V. Buck. 



Spirifer (part), of Eichivald and V. Buck. 



Porambonites, oi Pander, jyOrbigmj, M'Coy, and Sharpe. 



Spiriferes anormaux, a. yEauiRosTRES, De Verneuil.^ 



IsoRHYNCHUS, King, 1849.^ 



Orthis (part), Quenstedt. 



Animal unknown; shell circular, transverse or elongated, globose, sub-equivalve ; 

 valves articulating by teeth and sockets ; beaks slightly unequal, rather more produced 

 m dental valve, with a small area in each, generally rudimentary, and perforated by a 



^ Beitrage zur Geog. des Russischen Reiches, 1830. 



2 In the Geol. of Russia and the Ural Mountains, vol. ii, 1845. M. de Verneuil places the shells 

 belonging to Pander's genus among his abnormal Spirifers, forming two subdivisions, which he dis- 

 tinguishes as A. (squirostres {Porambonites) and B. Biforh, these last belonging to the genus Orthis. 



3 From being unacquainted with Pander's type and priority, Professor King proposed, in 1849, the 

 name Isorhynchus, which the author now admits to be a synonyme. 



