CLASSIFICATION OF THE BRACHIOPODA. 129 



Britain,' as supposed by that author. The only point on which great doubt may remain 

 is the propriety of admitting the term Orbicidoidea," proposed by M. d'Orbigny for a vast 

 number of fossil species, considered by the generaUty of authors to be true Discina, but 

 which the author of the ' Paleont. Frangaise' states to have been provided with a regular 

 pedicle, as in Terehratula; I am, however, convinced that many of the species thus denomi- 

 nated were attached, as in the typical Discince, and have had a portion of their pedicle 

 fibres extending over the external disk ; therefore, while introducing the term Orbiculoidea 

 as a sub-section, T do so with the greatest reserve and doubt, as no internal characters 

 have as yet been brought to bear on the subject. 



Geol. range. — It is highly probable that the genus Discina was represented during the 

 whole series of Geological periods up to the present day ; but according to M. d'Orbigny 

 the Palaeozoic and Secondary species are generically distinct, and Discina first appeared at 

 the Tertiary epoch, becoming more abundant in the present seas. 



Examples: D. lam€Uosa,^xoA.', /<«y/5, Sow,, sp.; 7iitida, Phil.; Townshendi, Forbes, sp. ; 

 Cumingii, Brod. ; strigata, Brod., sp. ; striata, Sow., sp. ; ? Morrisia, Dav., sp. 



? Section A. — Orbiculoidea, D'Orb., 1847.^ 



Type — 0. ELLIPTICA, Kutorga, sp. Int., PI. IX, fig. 253 — 255. 



Orbicula, of the generality of Authors. 

 Orbiculoidea, D'Orbigny, Be Rijclcholt. 

 ScHizoTRETA, Kutorga. 



Shell, sub-orbicular patelliform, longitudinally or transversely oval. Upper valve 

 conical with the vertex close to, or removed from the posterior margin ; loiver valve 

 conical or concave, no pedicle disk;? a narrow oval or circular aperture, more or less 

 confined in its shape, is situated in a furrow or depression. 



Obs. — M. d'Orbigny characterises his section as follows : — " Coquille de contexture 

 cornee non perforce, dont la valve inferieure concave est pourvue d'une ouverture later ale 

 au crochet pour le passage d'un pedicide simple ;'^ and supposes that these shells were 



^ In the Linn. Trans., vol. xiii, 1822. Sowerby falls into the same mistake made by Cuvier and 

 Lamarck ; since he considers the Patella anomala to be generically distinct from Crania. His obser- 

 vations relative to Lamarck's genus Discina seem essentially erroneous, as it is quite impossible the French 

 author could have traced his characteristic of Discina from a specimen of O. Norvegica, which is a Crania, 

 and therefore could not have presented the fissure and disk alluded to by the celebrated author above 

 noticed. 



- Cons. Zool. et Geol. sur les Brachiopodes, 1847. 



^ Considerations Zool. et Geol. sur les Brachiopodes ; Comptes rendus de I'Academie des Sciences, 

 August, 1847. 



* Cours El^mentaire de Pal. et Geol. Stratigraphiques, vol. ii, p. 90, 1852. The author states to be 

 acquainted with 27 fossil species. 



17 



