British Carhoniferous Producti. 561 



It has been found necessary to give a more detailed differentiation 

 of forms than that whicli appeared satisfactory to Davidson and 

 de Koninck, and consequently a number of new names have been 

 introduced. The genus Produchis, which appears to be certainly 

 polyphyletic, has been subdivided into several genera, and the author 

 has endeavoured to restrict the limits of the species and genera in 

 order that these fossils may be used with greater accuracy and 

 precision by both palaeontologist and zonal stratigrapher. 



In the present memoir only the pustulose and fimbriate forms are 

 described, as the author is most unfortunately unable to complete the 

 work he had undertaken. The introductory sections have, however, 

 been written with a view to the ultimate description of all the British 

 species. One of these sections is devoted to the history of the genus ; 

 this is followed by a discussion of the terminology. The terms adopted 

 are in agreement, as closely as possible, with those already generally 

 accepted. Much attention is paid to morpliological characters, such 

 as the development and functions of spines, the presence of ribs and 

 costae, the general shape of the shell, its internal features and shell 

 structure. 



Nomenclature and evolution are discussed at some length, though 

 not so full}'' as had been the author's original intention. The 

 important literature dealing with orthogenesis, homceomorphy, and 

 other problems of evolution is reviewed in a most interesting manner, 

 and copious references are given. 



In the section dealing with classification it is proposed to restrict 

 the name Productus to that group which contains the original 

 Anomites productus of Martin, and to separate the Producti, mainly 

 according to the nature of their ornamentation, into the following 

 sections, to each of which is given a distinct generic designation. 



Productus, J. Sow. Forms which are costate throughout all stages 

 of growth. Genotype, Anomites productus, Martin. 



Avouia, gen. nov. Forms which are spinose in the early stages but 

 develop costae at a later period. Genotype, Productus youngianus, Dav. 



Pustula, gen. nov. Forms which are essentially spinose in orna- 

 mentation. Genotype, Producta pustulosa, Phill. 



Buxtonia, gen. nov. Forms in which the young and adult stages 

 are characterized by a costate and spinose ornamentation, while in 

 old age spinosity alone is developed. Genotype, Anomites scahriculus, 

 Martin. 



Overtonia, gen. nov. This genus is founded upon internal pecu- 

 liarities of the brachial valve, the importance of which is discussed in 

 the definition. Genotype, Producta Jimhriata, J. de C. Sow. 



Prohoscidella, Oehlert. Geuot j-pe, Productus proboscideus, de Verneuil. 



Etheridgina, Oehlert. Genotype, Productus complectens, It. Ethe- 

 ridge, jun. 



The genus Daviesiella, Waagen, is not ranked with the above generic 

 divisions, as it is regarded as being more nearly related to the Chonetes 

 series. 



There are descriptions of twenty-three species of Pustula, of which 

 twelve are new, and one species of Overtonia. 



The work concludes with a comprehensive bibliography and index. 



DECADE VI. — VOL. I.— NO. XII. 36 



