ANIMALS. 85 



indivisus, medio submamillatus : alteras valvse candidissimus, rima transversa 



IVISUS, 



All the information that could be desired respecting the animal of this genus has 

 been published by Professor Owen, in his admirable paper on the Brachiopoda, under 

 the head of Orbicula lamellosa, Broderip. 



Discinas existed in the earliest organic ages, and have lived throughout all 

 subsequent periods up to the present time ; but never to any extent as species. They 

 now appear to be confined to the Pacific and Southern Oceans. 



DisciNA SPELUNCARIA, Sclilotleim, apud Goldfuss. Plate VI, figs. 28, 29. 



Oebicula speluncaeia, Schl. Handbuck der Geognosie, von H. T. de la Beche, 



p. 459, 1832. 



— — „ Geol. Man., 3d Eng. ed., p. 573, 1833. 



— — „ Phillips, Encyc. Metr., vol. iv, p. 615, 1834. 



— — „ Bull. Soc. Geol. de France, 2""= serie, vol. i, p. 30, 1844, 



— — „ Geol. Russ., vol. i, p. 222, 1845. 



— KoNiNCKi, Geinitz. Grundriss, p. 495, 1846. 



— SPELUNCABIA, Schl. King, Catalogue, p. 7, 1848. 



— — „ Howse, T. N. F. C, vol. i, p. 251, 1848. 



— KoNiNCKi, Geinitz. Versteinerungen, p. 11, pi. iv, figs. 25, 26, 1848. 



Diagnosis. — Form sub-orbicular. Upper valve moderately convex ; with the umbone 

 between its posterior margin and centre. Inferior valve flat ; with the fissure extending 

 from its centre to nearly the margin. Both valves marked with strong lines of 

 growth. 



The specific name herein adopted, having been applied by Schlotheim, according to 

 Goldfuss, to a Discina found at Gliicksbrunn, evidently identical with the species under 

 consideration, I prefer retaining it to adopting the one which has been subsequently 

 proposed by Dr. Geinitz ; particularly as the former name was current for a con- 

 siderable time previously to the publication of the ' Grundriss.' 



The specimen under figure 28, PI. VI, with two more, was found attached to the 

 small valve of a Productus horridus. 



he named B. ostreoides (? = Orbicula lamellosa, Broderip). Now, leaving out of view Cuvier's Orbicula, it 

 having been anticipated by Poll's Criopus (and subsequently confounded, through an error, with Lamarck's 

 Discina by most authors), I am disposed to recognise the three remaining genera; since the Crania 

 Egnabergensis is attached only by a portion of its under valve (it appears to have been only thus attached 

 when young) ; Criopus turbinatus is attached by the entire surface of the same valve ; and Discina ostreoides 

 is simply attached by a tendon or muscle passing out through a fissure in the under valve. By adopting 

 the genera Crania, Criopus, and Discina, as above typified, we not only preserve one or two names which 

 have been threatened with extinction ; but we arrange under the first head certain shells, such as C. spinulosa, 

 C. nummulus, C. antiquissima, which, from their imperfect mode of attachment, are obviously distinguished 

 from such completely attached forms as Criopus anomalus, C. turbinatus, C. Parisiensis, &c. Perhaps some 

 of the Cranidias above mentioned may hereafter be made typical of other genera. 

 ^ Animaux sans Vertebres, t. vii, p. 296, 1836. 



