BRACHIOPODA. 325 



Shell substance fibrous, strongly punctate. 



Type, Produdus Martini, Sowerby, =^ Anomites producfus, Martin, = Anomites 

 semireticulatus, Martin, i= Produdus semireticulatus, Martin. Lower Carboniferous 

 limestone to Coal Measures. 



Observations. It is the usage of sojne systematists to regard the genus 

 Productus as a starting point in the classification of the articulate brachiopoda 

 on account of the usual absence of the cardinal area and teeth. These are 

 features which are unquestionably in an obsolescent condition. It is rarely, 

 however, that some trace of them is not discernible, and it has been observed 

 by various writers, that they are sometimes well-defined, and that too in species 

 where they are normally wanting. For example, they may be present 

 in the species Produdus semireticulatus and P. Nebrascensis. In these features 

 Productus is degenerate, but this degeneracy has apparently not extended to 

 other points of structure, and the genus certainly lacks the simplicity of plan 

 in its structure so apparent in Orthis. Its late appearance in the Palaeozoic 

 and its close kinship to the CnoNETES-stock is evidence of its derivation from 

 that source. The earliest phase of the productoid type, which is abundantly 

 developed in the Devonian, and which has been distinguished by the name of 

 Productella, retains the articulating processes and cardinal area with persist- 

 ence throughout the period immediately preceding the appearance of normal 

 Productus. These features are, however, always more or less obscure, and 

 manifestly approaching desuetude. Leaving for the present the consideration 

 of this and the other generic or subgeneric divisions, which have been taken 

 from Productus, we have, in this genus, to deal with a very homogeneous 

 group of fossils. 



A grouping of the species of Productus was proposed by de Verneuil in 

 1845,* and this was amended and somewhat amplified by de Koninck in 1847. f 

 Dr. Waagen, in his magnificent treatise on the Producti of the Salt-Range, 

 is the latest writer who has discussed the genus at length, and has adopted 

 this classification with some modifications and additions ; it is evident that no 



* G^ologie de la Russie, p. 253. 



t Monographie du genre Productus, p. 29. 



