44 INTRODUCTION. 



his second order, Rudistes ; but, as justly observed by the author of the ' Paleonto- 

 logie Francaise,' De Blain villa's classification varies but little from that by Lamarck; and one 

 is at a loss to imagine what relation the celebrated malacologist could have found between 

 Plagiostoma, Dlanchora, and Terebratula. To the present day some authors are disposed 

 to consider the Rudistes as a portion of the Brachiopoda.^ While others, and by far the 

 greater number, repudiate such a conclusion.^ 



Eight or nine years after the publication of M. de Blainville's observations, Baron 

 Leopold von Buch issued his very remarkable work on the 'Classification of the Terebratulae;'^ 

 which materially contributed to the subsequent advancement of the science. The Baron, 

 founding his arrangements on the position and shape of the foramen, establishes two prin- 

 cipal divisions. In the first he places those forms attached by a pedicle issuing between the 

 valves {Jjingula), those with one valve perforated {Terebratula Belthyris), and those which 

 he considers to be imperforated {Calceola and Lejitcend). In the second division he 

 admits those species presenting a perforation through the middle of the lower valve {Discina), 

 or fixed by the substance of the same [Crania). 



About the same period, or shortly after, M. Deshayes proposed to divide the Brachiopoda 

 into two groups. In the first he included the articulated, in the second the unarticulated 

 species ;* but while geologists and conchologists were thus busily engaged framing 

 classifications on mere external and often deceptive appearances, our celebrated anatomist. 

 Professor Owen, was at work on the animal of some of the recent species,^ which tended 

 to consolidate and improve the foundation of the science by bringing to light important 

 zoological evidence. 



From 1834 to 1844® no very important change took place in the nomenclature, but 

 many new forms and interiors had been discovered which increased our knowledge of the 

 genera then existing, and pointed out the necessity for the creation of several others which 

 were introduced with more or less success by Prof. M'Coy, M. de Verneuil, Prof. King, M. 



^ Among these we may mention Goldfuss, D'Orbigny, Gray, &c. 



2 M. Deshayes strongly opposes the annexing of the Rudistes to the Brachiopoda. 



^ Since the Baron's researches much additional information has been obtained regarding the mode of 

 existence in the different species, and it seems now generally admitted, that no satisfactory arrangement 

 can be framed on the single evidence of the above-mentioned character. .411 Brachiopoda have lived 

 either free or fixed to submarine bottoms, by the means of a muscular pedicle, or by the substance of their 

 lower valve. Some species were attached during all their existence, others only when young, dispensing 

 with their attachment at a more advanced stage of life ; and in many examples of the same species the aperture 

 is entirely cicatrized in the adult. 



* Nouv. ed. des Anim. sans Vert, de Lamarck, vol. vii, 1836. 



' Trans, of the Zool. Soc, vol. i, 2d part, p. 141, 1835 ; and Ann. des Sciences Nat. Zool., vol. iii, 

 p. 31.5. 1845. 



•"' In M. Deslongchamp's 'Tableau Synoptique d'un Arrangement Systematique des Brachiopodes 

 Fossiles du Calvados,' 183": the perforation and deltidium are the chief characters made use of in this 

 classification. In 1841, Professor Phillips proposed the following arrangement of the Brachiopoda, 



