CLASSIFICATION OF THE BRACHIOPODA. 65 



a central mesial septum, which extends more or less into the interior of the shell. Structure 

 punctated. 



Obs. The animal has been admirably described and illustrated by Professor Owen in 

 the first chapter of this Introduction ; we need therefore only add, that the section was first 

 proposed by Professor King, who at the same time represented the muscular system which 

 he had described in 1846. As a section of Terebratula, I now believe the term Waldheimia 

 may be advantageously preserved, especially as the number of species possessing a long 

 loop is almost as great as that with a short one. 



Geol. range. — The exact period at which Terebratula with long loops first appeared is 

 as yet unascertained ; the interior of many Palseozoic species not having been examined, some 

 of which may possibly prove to belong to the section under consideration. Wuldhehnias 

 were, however, certainly represented from the Trias up to the present period. 



Examples : W.flavescens, Lamk., sp. ; lenticularis, Desh., sp. ; californica, Koch., sp. ; 

 longa, Roemer, sp. ; digona. Sow., sp. ; lagenalis, Schl., sp.; numismalis, Lam., sp. ; cornuta, 

 Sow., sp. ; resupinata. Sow., sp. ; Waterhousii, Dav., sp. ; Gragii, Dav., sp. ; cardium, 

 Lamk., sp. ; Moorei, Dav., sp. ; cranium^ &c. 



Genus — Terebratella, B'Orbigng, 1847.^ 



T]/pe — T. DORSATA, Lamarck, sp. Chilensis, Brod., sp. Int., PI. VI, figs. 11 — 14. 



Anomia and Terebkatula, of Authors. 

 Tebebratella, jyOrhigny? 

 Rhynchora (costata) ? Balman. 



Shell elongated or transverse, variable in shape : both valves regularly and unequally 

 convex or interrupted by a longitudinal depression in the smaller valve. Beak truncated 

 by an obhque foramen of a circular or oval form, and partly margined by a deltidium in 

 two pieces, at times disunited above the umbo : beak ridges more or less defined, and in 

 some cases leaving between them and the hinge line a flat or concave cardinal area : ex- 

 ternal surface smooth or variously punctated. Hinge articulating by the means of teeth in 

 the larger, and sockets in the smaller valve. In the interior of the ^ig^s. 



dorsal valve, under the cardinal process and hinge plate, a more or less 

 elevated medio-longitudinal crest or septum extends to about half the 

 length of the valve : the loop is elongated and doubly attached, first to 

 the hinge plate, and afterwards to the mesial septum, by processes given 

 off" at right angles near the centre of the valve, the remaining portion t. CMie^. 



^ In part i, pi. i, fig. 8 rf, I did not give sufficient development to the loop, which in this species is two- 

 thirds as long as the shell. 



' Considerations Zool. et Geol. sur les Brachiopodes. — Comptes rendus de 1' Academic des Sciences 

 Paris, 1847. — Annals des Sciences, vol. viii, 1847. — Paleont. Fran9. Ter. Cretac^s, vol. iv, p. 110, 1847. 



' Professor M'Coy's genus Delthyridea may have been intended for this section ; but on referring to 



9 



