PRODUCTA* 



^ESTA aequilatera, inaequivalvis, valva altera 

 plerumque convexa, margine inflexo, subrect^ 

 producto; altera plana, vel externe concava, 

 margine reflexo: margine cardinal! ti'ansverso. 



A Genus of fossil shells peculiar to the strata of secondary 

 formation, and to a certain extent characteristic of them^ 

 and particularly of the carboniferous or Mountain Lime- 

 stoile. The shells which compose it appear to have been 

 first brought into notice by Martin, in his Petrificata Der- 

 biensia, he called it Concliyliolithus Anomites, and defined it 

 as one of his divisions of the Genus Anomia^ and correctly 

 so, for there is no other Linnean Genus to which it could 

 be referred : later authors have, however, seen the pro- 

 priety of separating it from Anomia, as a well marked 

 and very distinct Genus, belonging to the Lamarckian 

 Brachiopoda, if we may be permitted to form our judgment 

 from the shell alone, for it is one of those genera of which 

 a recent specimen has never been seen, we cannot there- 

 fore hope ever to have an opportunity of examining tlie 

 animal. The shell itself is rendered remarkable by the 

 manner in which the anterior margin is produced beyond 

 the part inhabited by the animal, a circumstance, on 

 account of which, Martin gave to one species the specific 

 appellation of productus; a bad name, because equally 

 applicable to every species of the Genus, and therefore, 

 if it could have been applied as a generic name, would 



* We prefer retaining this name, though not strictly correct, changing how- 

 ever its termination to make it accord with Concha or Tes|;a, understood. Pro- 

 ducta is already adopted by Conybeare. (See Coaybeare and Phillips's Outlines 

 of the Geology of England and Wales.) 



