STUDIES IN rOEAMINIFERA 



27 



Barnard (1954, p. 384) made a study of the apertural 

 characters of specimens of Hantkenina from the Jackson 

 Eocene of Cocoa Post Office, Alabama, showing the 

 ontogenetic development of the multiple aperture of 

 the subgenus Cribrohantkenina. He concluded (p. 

 389): "The sub-genera are arbitrary divisions, and in 

 the opinion of the author the use of them should be dis- 

 couraged." 



We have examined large suites of specimens of many 

 species of Hantkenina from many areas and have found 

 none that show a gradation from the simple triradial 

 aperture of Hantkenina to the multiple aperture of 

 Cribrohantkenina. Furthermore, in our suite of speci- 

 mens from the area of the Cocoa Post Office the typical 

 H. alabamensis is much flatter; the sutures are moder- 

 ately depressed, straight, and radial; and the periphery 

 is entire. The associated "Cribrohantkenina bermu- 

 dezi" always has more inflated chambers and a lobulate 

 periphery, very deeply constricted sutures; and the 

 rounded openings of the midtiple apertinre are found 

 even on quite small specimens. We believe, therefore, 

 that Barnard was dealing with more than one species 

 but that aU the specimens he used to show a develop- 

 mental series of apertures belong to Cribrohantkenina 

 and do not show a gradation between this genus and 

 Hantkenina. 



There are other species of the Hantkenininae also 

 present at this locality, and Hantkenina brevispina Cush- 

 man resembles Cribrohantkenina bermudezi in possessing 

 much inflated chambers, but does not develop a multiple 

 aperture. Possibly specimens of this species of true 

 Hantkenina may have been considered as transitional 

 forms by Barnard. 



Typical Hantkenina is found from the middle to 

 upper Eocene, but Cribrohantkenina occiu-s only in the 

 upper Eocene. We therefore consider these two as dis- 

 tinct genera on the basis of different apertiu-al charac- 

 ters and different geologic ranges, although Cribro- 

 hantkenina imdoubtedly developed from Hantkenina. 



However, the subgenera Aragonella Thalmann, Appli- 

 nella Thalmann, and Hantkeninella Bronnimann are 

 much less distinctive, for a single species may show 

 considerable variation in the chamber shape, and in 

 the length of the spines and their apparent relative 

 position. Applinella was defined as differing from 

 typical Hantkenina in having the spines at the anterior 

 portion of the chambers, whereas those of Hantkenina 

 were nearly sutural in position. A glance at the final 

 chamber of each species shows that the spines are in 

 almost exactly similar positions, at the dorsal angle of 

 the chamber. The different appearance in earlier 

 chambers depends entirely on the amoimt of overlap 

 by the following chamber. When the wall of the final 

 chamber is attached just at the spine base of the pre- 

 vious chamber, the spine appears sutural in position. 

 When the wall of the final chamber is more restricted, 

 the preceding spine appears to be on the anterior 

 portion of the penultimate chamber. Also, the waU of 

 the final chamber may partially or wholly envelop the 

 spine of the preceding chamber, so that it may appear 



396818—57 3 



spineless, or the spine may even seem to be protruding 

 from the posterior portion of the final chamber. This 

 character varies considerably in a species and may 

 show some variation even on a single specimen. On 

 the specimens we have of H. alabamensis (topotype), H. 

 alabamensis primitiva (holotype), and H. (Applinella) 

 dumblei (lectotype), the early chambers show the spines 

 on the anterior portion of the chambers and not touch- 

 ing the following sutures, whereas the later chambers 

 show a stronger overlap and the spines "appear" 

 sutural. The final chamber is broken from the lecto- 

 type of H. dumblei, but the remnants of this final 

 chamber show an attachment partially enveloping the 

 base of the spine of the penultimate chamber. There- 

 fore, the basis for separation of Applinella seems to be 

 too variable in all these "subgenera" to be of value, 

 and we consider Applinella a synonym of Hantkenina. 



Hantkeninella was separated, as including only H. 

 alabamensis var. primitiva, whose early chambers lack 

 spines. Bronnimann (1950a, p. 417), in describing the 

 subgenus, stated, "At present it is the only known 

 Hantkenina with a spineless early stage and, therefore, 

 it cannot be referred to any of the existing subgenera." 



The development of spines is not an invariable 

 character in this group, however. We have large suites 

 of H. alabamensis including many specimens with non- 

 spinose early chambers. We also have some with early 

 chambers bearing spines and an occasional adult 

 chamber lacking any spine. Rare specimens also occur 

 with two or even three spines on a single chamber, both 

 in H. alabamensis and in other species. Some speci- 

 mens which are typical H. brevispina in aU other 

 characters lack spines on early chambers. In general, 

 the young forms of all species show shorter and less 

 well developed spines and, because of the amount of 

 variation in this feature, we do not consider their 

 absence on early chambers to be a diagnostic generic 

 character. Therefore, Hantkeninella is considered 

 synonymous with Hantkenina. 



Hantkenina differs from Schackoina Thalmann in 

 being planispiral, and in having a tripartite aperture, 

 with an elongate sht extending up the apertiu-al face, 

 whereas Schackoina has a very low arched aperture. 



Cribrohantkenina Thalmann differs in having multiple 

 areal apertures instead of a triradial, interiomarginal 

 equatorial apertiu-e bordered by lateral flanges. 



Types and Occurrence: Figured hypotype of 

 Hantkenina alabamensis Cushman (USNM P4791) from 

 the Pachuta formation, Jackson Eocene, Cushman's 

 "Cocoa sand," 1 mile southwest of the old Cocoa Post 

 Oflice, Choctaw County, Alabama. Collected by C. G. 

 Lalicker. Figured hypotype of H. alabamensis Cush- 

 man (USNM P4786) from the Pachuta formation, 2.2 

 miles south of Melvin, Choctaw County, Alabama. 



Holotype of Hantkenina alabamensis primitiva Cush- 

 man and Jarvis (Cushman CoU. 10067) from the 

 Eocene Mount Moriah beds, from bed of yellow 

 sandy clay directly underlying orbitoidal limestone of 

 VistabeUa quarry, Trinidad, B. W. I. Collected by 

 P. W. Jarvis. 



