2 BULLETIN 104, UNITED STATES NATIONAL MUSEUM 



Family 33. ROTALIIDAE 



Test generally trochoid except in Spirillina, all the chambers visible 

 from the dorsal side except in a very few genera which become par- 

 tially involute, only those of the last-formed whorl usually visible 

 from the ventral side; wall calcareous, usually rather coarsely per- 

 forate; aperture typically on the ventral side of the test. 

 • As restricted here, the Kotaliidae includes those calcareous per- 

 forate forms which are trochoid, with definite dorsal and ventral sides 

 and the aperture wholly ventral. The genera make a natural group- 

 ing closely related to one another, and the steps between the genera 

 often well fiUed by the simpler or more complex species. The family 

 may be derived through the conical forms of Spirillina and the simple 

 and more primitive forms of Patellina and Discorbis. The more 

 primitive genera have the umbilicus open, but this is filled in the 

 higher forms. The earlier genera have simple walls, the higher ones 

 as in Rotalia with double walls and a secondary canal system. There 

 is a gradual progression from very simple structures to those fore- 

 shadowing the specialized families which are derived from the 

 Rotaliidae. 



There are a few extinct genera but most of them are known from the 

 Cretaceous to the present seas. The geological history of the family 

 starts with Spirillina, which is recorded as early as the Cambrian. 



Some of the other simpler, more primitive genera had their begin- 

 nings in the Jurassic, but most of the genera do not appear until the 

 Cretaceous, while a number of the more specialized ones are not 

 developed until the Tertiary. There are a few records for certain 

 genera from the Paleozoic, but these are so far as can be made out 

 probably errors in the source of the material either through wrong 

 labeling or insufficient care in preparation of material. 



From the Rotaliidae have developed a number of specialized families, 

 several of which are included in the present part and the relationships 

 of which are sho\vTi in the Introduction to Part 6 of this bulletin. 



Subfamily 1. Spirillininae 



Test simple, consisting of a proloculum, and a planispiral, undivided, 



tubular second chamber, open end of the tubular chamber serving as 



the aperture. 



Genus SPIRILLINA Ehrenberg, 1841 



Spirillina Ehrenberg, Abhandl. k. Akad. Wiss. Berlin, 1841, p. 422. — 

 CusHMAN, Special Publ. No. 1, Cushman Lab. Foram. Res., 1928, p. 267. 

 Operculina (part) Reuss, 1849. 

 Cornuspira (part) Schultze, 1854. 

 Cydolina Egger, 1857 (not d'Orbigny). 



Genoholotype. — Spirillina vivipara Ehrenberg. 



Test tj^pically free, occasicnallj^ attached, planispiral, composed of 

 a subglobular or ovoid proloculum and a long undivided tubular 



