116 INTRODUCTION. 



genus ; the chief points of difference appear to consist — first, in the strongly articulated 

 hinge of Strophalosia, while no teeth or sockets have yet been noticed in any true 

 Productus, (such as P. semireticulatus, longispinus, giganteus, horridus, 8fc.,) where the 

 valves are entirely kept in place by muscular action : the cardinal process or boss so often 

 most improperly termed a tooth was simply a point of attachment for the cardinal 

 muscle, a view clearly pointed out by Professor King, and which I have been able to 

 verify in many recent forms of other genera. Secondly, by the presence of a well defined 

 double area and pseudo-deltidium, of which scarcely any trace exists in true Product^} 

 Internally, the muscular scars and reniform impressions seem also to offer some small 

 differences, but preserve the essential characters of Productus. 



Geol. range. — As far as our present knowledge goes, this genus first appeared in the 

 Devonian period, was sparingly represented in the Carboniferous epoch, and attained its 

 greatest numerical development in the Permian age, above which no authenticated example 

 has been yet discovered. 



Examples: St. Goidfussi, Munst., sp.; S. Morrisi ana, and Gerardi, King ; jnvductoides, 

 Murch., sp.; Buc/iiana, De Kon,, sp.; ? parva, King; ? sudacuteatas, Murch. ;^ &c. 



Sub- Section — Aulosteges, Helmersevi, 1847. 

 Type — A. Wangenheimi, Be Fern., sp. = A. variabilis, Heltn. Int., PI. IX, figs. 212 — 216. 



Orthis, sp., De Verneuil, 1845. 



Animal unknown ; shell of an irregular pentagonal shape, with its larger or ventral 

 valve, by far the most convex ; beak produced, and generally twisted either to the one or 

 the other side, and furnished with a well defined triangular area, longitudinally interrupted 

 by a pseudo-deltidium not quite reaching to the hinge line, which is straight and 

 not provided with articulating teeth; smaller or dorsal valve slightly convex at the 

 umbo, depressed or concave laterally ; cardinal edge more or less developed ; sm^face 

 of valves ornamented by a multitude of short tubular spires. In the interior of 

 smaller valve a large and produced trifid cardinal process extends under a portion 

 of the beak and deltidium, filling up the uncovered portion of the fissure, and serving 

 as a point of attachment to the cardinal muscle ; under this process a longitudinal 

 mesial ridge extends nearly to the margin, and on either side are placed the elongated 



^ M. de Koninck states that an area is nt times observable in some examples of Prod, giganteus and 

 punctatus ; but Professor King considers this appearance more deceptive than real, and only occasioned by 

 a strongly developed cardinal edge or margin ; the presence of a largely developed area and unarticulated 

 hinge in Aulosteges connects Strophalosia with Productus. 



2 This species is placed by Professor King in Strophalosia ; and it is worthy of notice, that 

 M. Bouchard had described the articulated hinge, area, and cardinal process, in a paper on this species, 

 in the 'Ann. des Sciences Nat.,' 1842. 



