66 GEOLOGICAL MEMOIRS. 



Terebratula Daleidensis, Rom. Leptaena Dutertii, Murch. 



Spiri/er Pellico.^ Serpula omphalotes, Goldf. 



Cabedanus.* Pentremites Pailletti, De Vern.* 



heteroclitus, Defr. (sp.)* Schulzii* 



Cabanillas.* Aulopora serpens, Goldf. 



Verneuili, var., Murch. Criserpia Michelini, Miln. Edw. 



Orthis resupinata, Mart, (sp.) Favosites polymorpha, Goldf. 



orbicularis, Sow.* fibrosa. 



crenistria, Phil, (sp.) var. ramosa. 



Leptaena Murchisoni, D'Arch. et De V.* Lithodendron caespitosum, Goldf. 



Note. — The species in italics are new ; and those to which an asterisk is at- 

 tached are described and figured by the authors in the original memoir above re- 

 ferred to. 



The relative preponderance of Brachiopoda is, it is well known, 

 the distinctive character of the Palaeozoic faunas, just as the pre- 

 ponderance of Cephalopoda, represented by Belemnites, Ammonites 

 and other of the siphoniferous multilocular genera, marks the se- 

 condary period. 



Among the Brachiopoda, of which two-thirds of the whole num- 

 ber of our series of Asturian fossils consist, those most remarkable 

 by their peculiar mode of development are the Terebratulae of the 

 group called Concentriccc, characterized by concentric striae more or 

 less lamellar, by the uniform absence of deltidium, and by a round 

 aperture at the beak of the ventral valve. The T. concentrica, V. 

 Buch, the type of the group, and a species found in the Devonian 

 beds of northern and western France, of England, Belgium, the 

 Eifel and Russia, does not however appear among these specimens 

 from Spain, although six species, one of which we have named T, 

 subconcentrica, from its very close resemblance to this typical form, 

 — a resemblance so near that it might almost be considered as a va- 

 riety, — form a link connecting it by common characters, although 

 gradually diverging from it more and more widely by successive 

 modifications. 



The presence of a medial furrow is the peculiar character which 

 connects these very different forms. This furrow, hardly appre- 

 ciable in T. suhconcentrica, which is distinguished from the type of 

 the group by its generally rounded, subelliptical and transverse 

 form, its large dimensions and the disposition of its striae, is seen to 

 be combined in the next species ( T. Pelapayensis) with a subpen- 

 tagonal and more elongated form, smaller dimensions, and a less open 

 angle at the apex. Still more decidedly indicated in T. Campoma- 

 nesii, the medial farrow is there accompanied by folds and lateral 

 furrows, and the front of the ventral valve is little different from 

 that of the dorsal one. The large and lamellar striae of this species, 

 present at all stages of growth, clearly distinguish it also from T. 

 Ferronesensis, where indeed the development of four plications on 

 each valve, separated by broad and deep furrows, the striae becoming 

 still finer and closer together, would fully justify the separation. 



Up to this point the forms had oscillated, if we may use the ex- 



