20 BRITISH OOLITIC AND LIASIC BRACHIOPODA. 



Genus — Spirifer, Sowerby. 1818. 



Shell unequivalved, equilateral, generally transverse, more or less trigonal, and convex. 

 Exterior rarely smooth, more often striated or costated ; larger valve always convex, often 

 gibbous, divided by a medio- longitudinal sinus, of more or less depth and width, cor- 

 responding with the mesial fold in smaller valve. Beak generally acute and straight, 

 sometimes recurved and obtuse, never truncated, area always triangular, more or less 

 elevated; thrown backwards, flat or concave, and divided by a mesial deltideal fissure, 

 always covered by a deltideum, notched at its base, for the passage of the peduncular fibres. 

 Smaller valve always convex, but less so than in larger valve ; longitudinally divided by a 

 mesial fold, elevated and proportioned to the sinus in larger valve, to which it corresponds. 

 No area, summit not much developed, extending a little beyond the rectilineal cardinal 

 edge ; hinge straight, transverse, formed of two diverging teeth, limiting the base of the 

 deltoid fissure of larger valve, and placed in the sockets existing on each side of the beak 

 of the smaller valve; internal calcareous supports formed by two lamellae, arising from 

 under the beak of smaller valve, and forming a number of spiral coils, diminishing in size 

 towards the cardinal angles. 



Obs. Several divisions have been proposed in the Genus Spirifer, to which we will allude 

 in our introduction, and shall only notice here, that the punctuated character believed 

 to be peculiar to Lias Spirifers {Spiriferina, D'Orb.), also exists in those of other epochs. 

 In our British Oolitic series, we are only acquainted with four species of Spirifer : viz., 

 Spirifer rostratus, Sp. Ilminsteriensis, Sp. Walcottii, and Sp. Miinsterii, all found in the 

 lias. And on the Continent four or five more have been discovered ; so that this genus, 

 which has not yet been known higher up in the series, was represented by eight or nine 

 forms, some of which are very similar in exterior appearance to more ancient types. 



17. Spirifer rostratus, Schl. Plate II, figs. 1 — 21 ; Plate III, fig. 1. 



Terebratulites rostratus, ScJdotheim. 1822- Nacli. Zur. Petrefact., pi. xvi. 

 Deltiiyris verrucosa, V. Buck. 1831. Petrifications Remarquables, pi. vii, fig. 2. 

 Spirifer rostrata, Zieten. 1832. Die versteinerungen Wurttemberg, p. 38, fig. 3. 



— mesoloba, 1 Phil. Deslong champs. 1837. Soc. Linn, de Normandie. 



— Hartmanii, Zieten. 1838. Die Verst Wurttemberg, pi. xxxviii, fig. 1, 



— verrucosa, Zieten. 1838. Die Verst Wurttemberg, pi. xxxviii, fig. 2. 



— pinguis, Zieten. (non Sow.) 1838. Die Verst Wurttemberg, t. xxxviii, fig. 5. 

 Deltiiyris rostratus, V. Buch. 1840. Class, et descrip. des Deltiiyris, Mem. Soc. 



Geol. de France, l ere Serie, t. iv, pi. 10, fig. 24. 



— verrucosa, V. Buch. 1840. Class, et descrip. des Deltiiyris, Mem. Soc. 



Geol. de France, 1"" Serie, t. 4, pi. x, fig. 30. 



— tumidus, V. Buch. 1840. Class, et descrip. des Deltiiyris, Mem. Soc. 



Geol. de France, l ere Serie, t. 4, pi. x, fig. 29. 



