58 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1919. 



showing their subequal form and straight 

 dividing wall. 



Morton's Nummulites manteUi was taken 

 by Gumbel as the type species of his genus 

 Lepidocyclina, and it is therefore especially 

 important to fix this species very definitely. 

 Fortunately, as already noted, although no 

 type specimen is available, the published data, 

 though meager, are nevertheless sufficient. 

 Morton's description,' "Flattened, thin, be- 

 coming sharp at the edge, and having a central 

 pustuloid elevation, diameter from half an 

 inch to an inch and a half," combined with 

 the figm-e, is enough to determine this species, 

 which is "innumerable in the whitish loose- 

 grained limestone near Claiborne, Ala." 



The diameter given by Morton, half an inch 

 to an inch and a half, and b}" Lemome and 

 R. DouviI16, 25 to 35 millimeters, gives the 

 maximum size almost exactly. In fact, where 

 there is an abundance of the material it is 

 most striking to see the very slight range of 

 diameter of well-developed specimens away 

 from 35 millimeters. As may be supposed, 

 from what is known of the life history of 

 recent Foraminifera, the great mass of adult 

 fossil ForamiiTifera represent not animals that 

 have died from usual causes but individuals 

 that have divided their cell contents in the 

 reproductive process and left the test empty. 

 This process, taking place at a certain stage 

 in the life history of the individual, leaves an 

 abundance of empty tests of adults and com- 

 paratively few tests of yoimg individuals in 

 the same bottom sample, and therefore accounts 

 for the great abundance of mdividual tests 

 of the maximmn adult size. 



In 1890 De Gregorio - gave four "mutations" 

 of " Orbitoides inanteUi." His figm-es 16 and 

 17 are copied from the originals of Morton, 

 and of the other illustrations, figures 21 to 26, 

 which show the "mutation" (text) or "var." 

 (explanation of plate), called by De Gregorio 

 "umirellopsis," represent the Cypical L. man- 

 teUi. Figures 21 to 23 are not well character- 

 ized but are sufficiently so, and figures 24 to 

 26 are very typical of the early stages of L. 

 mantelli. The description, "Papyracea, dila- 

 tata, exihs, in medio xitroque latere vix sub- 

 tuberculata," certainly adds nothing to dis- 



• Am Jour. Sci., vol. 23, p. 291, 1833. 



> Annales g(^ol. paMont., vol. 8, pp. 2G1, 262, pi. 46, figs. 10-32, 1890. 



tinguish this from typical L. mantelli. More- 

 over, De Gregorio leaves no form for the 

 typical, dividing all his material into the four 

 "mutations." Therefore it seems reasonably 

 certain that var. umhreUopsis De Gregorio is 

 but a synonym. Of the other three "muta- 

 tions," the figures of which are evidently 

 much enlarged from small specimens, little 

 need be said here except that they evidently 

 are neither L. mantelli nor forms of that species. 



As is shown by the records, L. manteUi is 

 characteristic of certain definite horizons near 

 the base of the Oligocene in Alabama, parts 

 of Mississippi, and northwestern Florida. From 

 all the material examined it seems to occur 

 usually alone, without other species of its 

 group, a peculiarity that distinguishes it from 

 certain species of similar size in the upper 

 Eocene. 



It has been suggested that the absence of 

 pillars in this and other species is evidence of 

 a primitive character, but this I do not think 

 necessarily true. L. mantelli occurs geolog- 

 ically later than other species that show very 

 strongly developed pillars, and, as noted in 

 the description of L. georgiana, a condition 

 lacking pillars may follow an early develop- 

 ment in which pillars were characteristic. 

 From this evidence, and the fact that the 

 umbo in the adult shows a tendency to flatten, 

 it would seem that L. mantelli may be really 

 a senescent species rather than a primitive one. 



In every lot of material in which the species 

 occurs in considerable numbers a very few speci- 

 mens are found which exceed the normal maxi- 

 mum diameter of 35 millimeters. These range 

 from 38 to 41 millimeters, and their rarity, 

 together with their larger size, seems to indicate 

 that they are the microspheric form of the 

 species. The embryonic chambers are not 

 showai clearly, although present in the larger 

 specimens (PI. XIII; PI. XIV, fig. 1). Lemoine 

 and R. Douville record the occurrence of both 

 microspheric and megalospheric forms but 

 give no data as to their relative size. 



In the iVmerican literature the name '^Orbi- 

 toides mantelli" has covered manj" things, and 

 it is evident from the material in various collec- 

 tions that the name has been used very loosely. 

 The list of stations given here will serve to 

 check those references in the literature in which 

 they are mentioned. References to other sta- 



