96 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1K\. 



Genus DISCORBIS Lamarck, 1804. 

 Discorbis byramensis Cushman, n. sp. 



Plate XIX, figures 0^8. 



Test, pyramidal, low, octagonal, ventral side 

 slightly concave, peripheral margin subacute: 

 eight chambers in each of the four or more 

 coils, their margins uniting to form a series of 

 eight ribs extending radialh' from the apex of 

 the test to the periphery, the lateral sutures 

 much less distinct, surface between the ridges 

 concave but smooth; ventral surface composed 

 of numerous radiating rounded costae broken 

 up transversely to form a beaded surface; 

 umbilical area hollow; aperture at the base of 

 the last-formed chamber. Diameter 0.35 to 

 0.40 millimetei-, height 0.10 millimeter. 



This well-characterized species is very rare 

 in the marl at Byram. It is probably nearest 

 in its affinities to D. corrngata Millett, described 

 from specimens obtained in the Malay Archi- 

 pelago and recorded by Heron-Allen and Ear- 

 land from the Kerimba Archipelago, off the 

 southeastern coast of Africa. D. corriigata 

 seems to have but half as many chamliers to a 

 coil as D. bijrcunensis and is much higher in pro- 

 portion. The Kerimba specimens show the 

 sutural lines, but the Malay specimens do not. 

 This species is also recorded by Heron-Allen 

 and Earland from Sandoway, Arakan coast, 

 Burma, and Rottnest Island, West Australia, 

 thus having a wide Indo-Pacific range. In the 

 characters of the ventral surface it is also re- 

 lated to D. patelliformis H. B. Brady and D. 

 tahernacularis H. B. Brady, both typical Indo- 

 Pacific species. 



With the geographic relationships of D. hy- 

 ramensis its occurrence in the lower Oligocene 

 of Mississippi is very interesting. 



Discorbis orbicularis (Terquem) Bertlielin. 



Plate XIX, figures f». 10. 



Rosal'ma orhicularis Terquem, Essai siu' le classement des 



animaux qui \dvent siu- la plage de Dunkenjue, 



faae. 2, p. 75, pi. 9, figs. 4a, b. ISVu. 

 Discorbis orhicularis (Terquem) Bertlielin, Liste des 



foraminiferes recueillis dans la liaie de Borgneuf 



et a Pornichet, p. 39, No, 63. 1S7S. 

 Cusliman, U. S. Nat. Mus. Bull. 71, pt. 5. p. Ki. pi. 11, 



fig. 1; figs. 18a-c (in text). 191.5. 

 Discorhina orbicularis (Terquem) H. B. Brady, Chnllengcr 



Rept.. Zooyogy, vol. 9. p. 647, pi. SS, figs. 4-8, 1884 



(and numerous subsequent authors). 



A few specimens of the broad, flat, scalelike 

 form that is common in shallow water of tropi- 

 cal and subtropical seas were found in the marl 



at By ram. They are here referred to D. orhicu- 

 laris Terquem, although the number of cham- 

 bers is much less than in the usual form of that 

 species. All the specimens are of similar size 

 andcharacter. Diameter 0.55millimeterorless. 

 The figures of specimens referred to this 

 species by various authors show a considerable 

 range of form and charactei-. 



Genus TRTJNCATULINA DOrbigny, 1826. 

 Truncatulina lobatula (Walker and Jacob) D'Orbigny. 



Plate XX, figures 1-3. 



" Nautilus spiralis lobatus, etc.," Walker and Boys, Tes- 

 tacea minuta rariora, p. 20, pi. 3, fig. 71, 1784. 



Nautilus lobatula Walker and Jacob, Adams's Essays on 

 the microscope, Kanmacher's ed., p. 642, pi. 14, fig. 

 36, 1798. 



Truncatulina lobatula (Walker and Jacob) D'Orbigny, in 

 Barker, Webb, and Bert helot, liistoire naturello 

 desiles Canarias, vol. 2, pt. 2, Foraminiferes, p. 134, 

 pi. 2, figs. 22-24, 1839; Foraminiferes fossiles du 

 basein tertiaire de Vienne, p. 168, pi. 9, figs. 18-23, 

 1846. 

 H. B. Brady, Challenger 'ReT[>t., Zoology, vol. 9, ]>. 660, 

 pi. 92, fig. 10; pi. 93, fig. 1, 1884. 



Specimens of an abundant form in the Byram 

 marl are referred to this species. In most of 

 them the last half of the final whorl is some- 

 what angled so that a shallow depression is 

 formetl on the dorsal surface. The ventral 

 surface is well rounded. This is a very wide- 

 spreail species, but from the appearance of the 

 fossil forms from various horizons it may have 

 more than one form. 



It has been recorded from the Pliocene 

 (Waccamaw formation) at Cronly, N. Cj^rom 

 several Miocene formations in Maryland, Vir- 

 ginia. South Carolina, and Florida,' and from 

 the Miocene of Santo Domingo." 



Truncatulina byramensis Cushman, n. sp. 



Plate XX, figures 4-6. 



Test planoconvex, dorsal side slightly con- 

 vex, veiatral side flattened, peripheral margin 

 subcarinate; about eight chambers in the last- 

 formed whorl, chambers on the ventral side 

 failing to reach the center of the test, leaving a 

 definite umbilical area which is filled with 

 clear shell material; on the dorsal side each 

 chamber at its inner border has the angles 

 somewhat produced and a broad, roimded 

 reentrant near the middle; on the ventral side 

 the inner haff of the chamber is rather in- 



6U. S. Geol. Survey Bull. 67fi, p- 16, pl. 1, fig. 10, 191S 



' Idem, p. 60, pl. 17, figs. 1-.1. 



'CariicRie Inst. Washiiigtou Puh. 291, p, 41, 1919. 



