PRODUCTUS (Lat. productus, prolonged, led forward, p.p. of produccre, to lead forward, pro duce). An important genus of fossil brachiopods found in Upper Devonian and especially in Car boniferous rocks, The shells are usually semi circular in outline, with straight hinge-line, con cave or flat dorsal and very convex ventral valve, both of which are often much produced anteriorly. The beak of the dorsal valve is depressed, while that of the ventral valve is very prominent and often projects far behind the hinge-line. The outer surface has radial or concentric wrinkles and the ventral valve has generally a number of long curved hollow spines by which the shell was anchored to the muddy or sandy bottom. The genus Productus is a well-known index of the system. Prouuctus sciaircticu t us of the Subcarboniferous limestone has been found ill almost all parts of the word; it is per haps the most widely distributed fossil mollusk known. Another species. Productus horridus%
is characteristic• of the Coal measures. Product/is giyontcus, with a width of six to ten inches. is the largest brachiopod known. A number of allied genera of interest are: Productella, the Devonian ancestor of Productus, a less degenerate type with cardinal area and teeth; Proboseidala, a Carboniferous phylogerontie type in which the an terior portion of the ventral valve is much pro duced to form a sort of siphonal tube; Stropha losia, a degenerate type, found in the Devonian and Carboniferous. which by cementation of its ventral valve to foreign objects has lost its sym metry of form. Consult Hall and Clarke, "In troduction to the Study of the Genera of Palmozoic Brachiopoda," in Pahrontology of Yew Fork, vol. viii., part 1 (Albany, 1892).