SPECIES OF CAMERINIDAE — BARKER 307 



and the West Indies," in which some new Mexican forms, hitherto 

 unpublished, are described and figured. I have traced 50 recognized 

 species of the genera Nummulites {Camerina), OpercuUnella, and 

 OpercuUnoides described from the Americas, but it is not considered 

 necessary to list these here, beyond stating that careful comparison 

 has been made in the case of all Mexican forms with those previously 

 found in the New World. 



CLASSIFICATION 



The Camerinidae possess the most extensive literature of any group 

 of Foraminifera, so it is not proposed to give here long bibliographic 

 lists, but only the more important references to American species. 



The question of nomenclature is a difficult one, the accepted custom 

 being to follow d'Orbigny in allotting the various species to the 

 genera Nummulites {Camerina of Bruguiere), Operculina, and As- 

 silina, with the addition of Yabe's genus OpercuUnella for such 

 forms as appear intermediate between Camerina and Operculina. 



The establishment of Nummulites or Camerina for completely in- 

 volute forms with lateral spaces between successive laminae, Opercu- 

 lina for completely evolute forms, and Assilina for forms that are 

 involute but lacking the lateral cavities, the laminae being thin and 

 closely appressed, seems at first to be a simple and clearly defined 

 system of classification. Unfortunately, a certain number of species 

 commence with an involute spire and later open out becoming com- 

 planate and evolute. Such forms were included by d'Orbigny and 

 by Brady (see classification of the Nummulinidae in the Challenger 

 Report) in Operculina, since the definition clearly states that the 

 early whorls may be more or less embracing. Yabe, however, pre- 

 ferred to take such forms out of Operculina into a new genus Oper- 

 culinella, producing more confusion, as individual ideas as to the 

 characters of the new genus seem to be greatly varied. 



Furthermore, none of the genera satisfactorily fitted the majoritj'^ 

 of American species, which are thin, of few whorls, complanate, and 

 nearly always completely involute, without lateral cavities. As a 

 result species have been variously attributed to Camerina, Num- 

 m.ulites, Assilina, OpercuUnella, and Operculina according to the 

 opinion of each individual author. In 1935 Hanzawa erected the 

 genus OpercuUnoides for the American group of species mentioned 

 above ; he refers a number of species to the new genus, on the evi- 

 dence of actual specimens and on the original figures (Hanzawa, 

 1935. pp. 16-19) but does not illustrate the new genus, and the de- 

 scription might well be amplified. The genotype is given as Oper- 

 culinoides icillcoxii (Heilprin), and most American species formerly 

 considered to belong to Operculina are transferred to OpercuUnoides. 



