FAMILY 22. LAGENIDAE 195 



always known nor what are the limits of range in these various 

 "genera". A study particularly of Jurassic material where the 

 Lagenidae are especially abundant will help to settle such prob- 

 lems. With abundant Jurassic and Cretaceous material it would 

 make an excellent problem for critical research to work out 

 carefully the relationships in this group. 



Hemicrist ell aria Stache, 1864 and Hemirohulina Stache, 1864 

 were erected for the uncoiled forms with radiate and robuline 

 apertures. They merge into Marginulina and Saracenaria. 



Frondovaglnulina Dettmer has the early chambers much 

 compressed and bilaterally symmetrical but the later chambers 

 are added at one side as in Vaginulina. Staffia Schubert has 

 the early chambers Nodosaria-like, and later ones frondicularian. 

 Tribrachia Schubert has RJiabdogonium-like early chambers and 

 the later ones frondicularian. Spirofrondicularia Schubert has 

 the early chambers Polymorphina-like, and the later ones 

 frondicularian. Flabellinella Schubert has the early chambers 

 Vaginulina-like, and the later ones frondicularian. 



The subfamily Lageninae contains those single-chambered 

 forms which have arisen through the megalospheric form of 

 embracing species of Glandulina. Those species with 

 Entosolenian tubes and narrow curved apertures do not belong 

 here but are end forms of the Ellipsoidinidae. Others of the 

 group also are end forms derived in a similar manner from the 

 Buliminidae and other families, but need careful research on 

 abundant material to be placed with accuracy. It is a complex 

 group which shows its position at the end of a line of develop- 

 ment by the excessive ornamentation that has been developed. 

 This is not true of the more recently acquired single-chambered 

 condition in the Ellipsoidinidae which are still smooth like most 

 of the other members of the family. 



It is possible that Robulus with its larger aperture represents 

 the primitive stage and the original aperture of the early coiled, 

 single-chambered ancestor. The family was abundant in the 

 Jurassic and Cretaceous and has developed few new characters 

 since that time. Frondicularia and allied forms reached their 

 climax in the Cretaceous. 



