ANIMALS. 87 



vol. i, p. 153, it is necessary to consider the Condi. Anomites produdtts, of Martin, 

 as its type. 



Although this remarkable genus possesses in its external (concavo-convex) form a 

 striking resemblance to certain species of Strophomena and Leptana, it is nevertheless 

 easily distinguished from them by the want of teeth, and an area, and by the surface 

 of its valves (the large one in general, and the small one occasionally) being 

 furnished with spines. So far as is yet known, Chonetes is the only long-established 

 genus likely to be confounded with Prodicdiis, on account of its being spiniferous ; but 

 in the former the spines are confined to the cardnial margin. 



Late researches have proved the Silurian existence of this genus. Prof. M'Coy first 

 described two species, Produdiis moniliferus and P. tenuidndatus, in the Silurian rocks 

 of Ireland;' Mr. Davidson next described a species, P. Twamlcyi, discovered by 

 Mr. Gray in the Dudley Limestone \ and at the same time M. de Verneuil published a 

 full description of another species, P. {Leptmia) enigma, found in the " inferior Silurian 

 Limestone of Osmundberg, in Dalecarlia."'" The genus Produdm may therefore be said 

 to have commenced its existence in the earliest known organic age ; and considering 

 that no remains have yet been found in rocks more recent than the calcareous Marls of 

 St. Kassian,* it may be said to have become extinct about the early part of the secondary 

 period. Productuses do not appear to have existed to any extent until a considerable 

 time after their first creation, since the greatest number of known species belong to 

 the Carboniferous system. 



Productus HORRiDus, /. Sowcrhj. Plate X, figs. 29, 30, 31 ; PI. XI, figs. 1, 2, 3, 

 4, 5, 6, 7,8,9, 10, 11, 12, 13. 



Versteinerter Grypiiit, Iloppe, Kurze Beschreibung Verst. Grypli., &c., 1745. 

 Gespaltene GRYniiTEM, Kr.orr et Walch. Naturg. der Verst., vol. ii, p. 79, pi. B, i d, 



figs. 5, 6 ; pi. D, figs. 1-3, UHS. 

 — — Walch. Das Steinreich, vol. i, p. ICO, pi. xix, fig. 2, 2d edi- 



tion, ] 709. 

 Grypiiitex von Gera, Schr'uter. Journ. fiir die Leibli. des Steinr., vol. ii, p. 326, pi. i, 



fig. 5, 1775. 

 'Gespalten Gryphiten, ,, Lithol. Real u. Verballexik, vol. ii, p. 309, 1779. 

 Geraische Gryphiten, Walch. Der Naturforscher, vol. xiv, p. 24, 1780. 

 Gryphit MIT Staciieln, Schlotheim. Gesells. Naturf. Freunde zu Berlin, vol. iv, p. 75, 



pi. ii, fig. 1, 1810. 



1 A Synopsis of the Silurian Fossils of Ireland, p. 25, 1846. 



2 Bulletin de la Soci^te Geologique de France, t. v; seance du 5 Mai, 1848. 



* Idem. 



* Herrn von Klipstein notices three species occurring in the St. Kassian beds. (Vide Karsten und 

 Dechen, Archiv fiir Min., Geog. &c., 1843, p. 352.) Dr. de Kouinck only notices one species (Productus 

 Leonhardi) in his ' Monographic du genre Productus.' 



