374 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



in size, and the chambers very narrow and much curved. The type 

 specimen is a fossil from the region of Bordeaux. 



Although many writers have referred many things to this species, 

 a study of the Philippine collection does not show anything which 

 may be reasonably referred to this species as shown by d'Orbigny. 

 Therefore, as far as the Philippine species are concerned, the name 

 is not available. A study of the other species described since 

 d'Orbigny 's time shows several names, none of which can well be 

 applied here. As a rule the various forms of Operculina have been 

 divided by various authors into smooth forms, which are referred 

 to Operculina complanata, and into those showing granular orna- 

 mentation, which are usually assigned to Operculina granulosa 

 Leymerie, either as a species or variety of 0. complanata. Such a 

 treatment is a very simple way to dispose of the entire matter. 

 However, the study of the thousands of Philippine specimens has 

 shown that there is no such general and simple rule which can apply 

 to all the specimens obtained. Also a study of the type figure and 

 description of 0. granulosa by Leymerie, which was a fossil from 

 Europe, shows that it is a very close-coiled form, apparently with 

 rows of beads on the sutures. Such a form is possibly known from 

 a few stations in the Philippines, and for this the name 0. granu- 

 losa is restricted. Of the other forms two may take their names from 

 the species named by d'Orbigny, and later figured in Fornasini's 

 publication of the "planches in^dites."^^ The first of these to which 

 d'Orbigny gave the name 0. gaimairdi, was from ''Rawack, Nou- 

 velle-Hollande." That would be in a closely related area to the 

 Philippine faunal region, and a form very close to this occurs abund- 

 antly at a number of stations with definite geographical limitations. 

 Another group is similar to that figured by d'Orbigny and named 

 by him Assilina discoidalis. This has a large protuberant center, 

 with numerous granules, followed by raised sutures, the whole with 

 a definite keel and the revolving whorls thickest near the middle. 

 Such forms are very abundant at a few stations in the Sulu Archi- 

 pelago, but are very rare elsewhere. The type station for this 

 species is Rawack. 



Carpenter also mentions and figures a form from the Philippines 

 very similar to this. For such forms the name 0. discoidalis can be 

 used. 



In studying the large collection of Operculina each station was 

 taken separately, and in this way it was possible to recognize a num- 

 ber of minor forms or races which seem to have a definite geo- 

 graphical distribution. The genus is best developed in compara- 

 tively shallow water but some of the large forms reach considerable 

 depths. 



M Boll. Soc. Geol. Ital., vol. 22, 1903, pi. 14, figs. 4, 8. 



