1915- No. 12. THE STROPHOMESIDAE OF THE KRISTIANIA REGION. I3 



have fam. Strophomenidae, embracing the genera Orthidium Hall. Stro- 

 phomena Blais (Raf.), Derbya \V.\agex, Meekella White & St. J.. Strepto- 

 rhynchns Kino, Orihothetes Fisch.. Hipparionvx \'anlxem. Kayserella Hall, 

 Triplecia Hall, Mimttltis Barr., Streptis Dav. — , and fam. Leptauidœ 

 with Leptœna Dalm., Rafmesqiiina Hall, Stropheodonta Hall, Brachy prion 

 Shaler. Douvillina Oehlert. Leptostrophia Hall, Pliolidostrophia Hall, 

 Stroplionella Hall, Amphistrophia Hall, LepUlla Hall, Pledambouites 

 Pand., Christiania Hall, Lrptanisca Beecher, Davidsonia Bouchard. 



Since Hall and Clarke's work was published, we have had several 

 valuable lists of classifications from Prof. Schlchert's hand, and we find 

 there the Strophomenidae in the restricted sense as one family, and this 

 view now seems to be generally accepted in America. The difference 

 between genera like Rafinesqtiina Hall and Clarke and Strophomcna 

 Blainv. is certainly also of quite another, inferior character, than that 

 between Rafinesquina and Orihis. 



Schlchert. however, has divided the Strophomenidae in different 

 minor groups or subfamilies, each embracing a number of genera that are 

 mutuall}' related. This dividing of the Strophomenidae into subfamilies 

 will be discussed under »General results« in a later chapter of this paper. 

 In the following the fossils will be arranged after genera only. 



With regard to generic names, in the following pages the newer 

 American nomenclature will be employed. The latter has encountered a 

 considerable amount of opposition from European paleontologists, amongst 

 whom the Davidson system with the name Strophomcna in the widest 

 application of the term, has prevailed until recent ^ears, and in fact is 

 still largel}' employed. However, in view of the great wealth of species 

 belonging to Strophomcna — according to Davidson's nomenclature — 

 that American investigators have revealed, it must be considered justifiable 

 to subdivide this genus on the basis of the special characters indicated bv 

 Hall and Clarke. In certain cases, perhaps, a separation into sub-genera 

 instead of into genera might be preferable: that, however, is a matter of 

 individual judgment, and it is of minor importance whether we prefer one 

 method or the other. The fact that diagnosis cannot always be made 

 with absolute precision, and that — for instance — we may be in doubt 

 as to which genus a species should be referred, does not impede the justi- 

 fication of a system of classification, since such conditions may occur in 

 all natural classification. J shall recur to these questions in the final 

 chapter of the present work. 



