STUDIES m FORAMINrFERA 



43 



cal in position but covered by a spiral system of tegilla, 

 accessory intralaminal and infralaminal apertures 

 present. 



Range: Upper Cretaceous. 



Abathomphalus BoUi, Loeblich, and Tappan, new genus 

 Plate 11, Figures la-c 



Type species: Globotruncana mayaroensis Bolli, 

 1951. Derivation: Abathes, Gr., shallow + omphalos, 

 Gr., umbilicus; gender, masculine. 



Test free, trochospiral, biconvex to concavoconvex, 

 almost nonumbilicate, periphery with a single or 

 double keel; sutures depressed, curved and sometimes 

 beaded on the spiral side, depressed and radial on the 

 umbilical side; wall calcareous, perforate, radial in 

 structure, commonly ornamented with fine nodes, and 

 the peripheral keels and sutures may also be beaded; 

 primary apertm^e interiomarginal, extraumbilical, as a 

 rule covered by a continuous umbihcal tegillum of 

 irregular outline, with accessory infralaminal apertures 

 situated at the suture contacts with the tegillum. 



Remarks: Abathomphaliis, new genus, differs from 

 Globotruncana Cushman in lacking a wide and deep 

 imabilicus with a sharply angled rim and deUcate tegilla 

 extending from each chamber and in the interiomar- 

 ginal, extraumbilical position of the primary aperture. 



In Abathomphalus, new genus, the umbilical area is 

 not open, the final whorl of chambers all meeting 

 ventrally, although their junction may be obscured by 

 the single umbilical tegillum, which appears to be an 

 extension from the final chamber. The accessory 

 apertures are always infralaminal, not both infralaminal 

 and intralaminal as in Globotruncana. 



Abathomphalus, new genus, differs from Globorotalia 

 Cushman in the presence of the tegillum and accessory 

 infralaminal apertures. It differs from Rotalipora 

 Brotzen in lacking the secondary sutural apertures on 

 the umbilical side, in having a tegillum and accessory 

 infralaminal apertures. 



Types and occurrence: Holotype (Cushman Coll. 

 59685) and paratypes (Cushman Coll. 59686) of 

 Abathomphalus mayaroensis (Bolli) from the Maestrich- 

 tian (Abathomphalus mayaroensis zone), Guayaguayare 

 formation, subsurface section in the Guayaguayare 

 area, Trinidad, B. W. I. 



Figured hypotype (USNM P4833) and unfigured 

 hypotypes (USNM P4833, P4861, P4862 and P4863) 

 from the Maestrichtian Guayaguayare formation (Aba- 

 thomphalus mayaroensis zone), from a subsurface core, 

 Guayaguayare area, southeastern Trinidad, B. W. I. 



Range: Maestrichtian. 



Genus Rugoglobigerina Bronnimana, 1952 



Plate 11, Figures 2a-5c 



Rugoglobigerina Bronnimann, Bull. Amer. Paleontol., vol. 34, 

 No. 140, p. 16, 1952. 



Plummerella Bronnimann (not Plummerella DeLong, 1942), 

 Bull. Amer. Paleontol., vol. 34, No. 140, p. 37, 1952. (Type 

 species: Rvgoglobigerina (^Plummerella) hantkeninoides hant- 



keninoides Bronnimann, 1952. Fixed by original designa- 

 tion.) 



Plummerita Bronnimann, Contr. Cushman Found. Foram. Res., 

 vol. 3, pts. 3, 4, p. 146, 1952 (new name for Plummerella 

 Bronnimann, 1952). 



Trinilella Bronnimann, Bull. Amer. Paleontol., vol. 34, No. 140, 

 p. 56, 1952. (Type species: Trinilella scotti Bronnimann, 

 1952. Fixed by original designation and monotypy.) 



IKuglerina Bronnimann and Brown, Eclog. Geol. Helvetiae, 

 vol. 48 (1955), No. 2, p. 557, 1956. (Type species: Rugoglo- 

 bigerina rugosa rolundala Bronnimann, 1952. Fixed by 

 original designation and monotypy.) 



Type species: Globigerina rugosa Plummer, 1926. 

 Fixed by original designation. 



Test free, trochospiral, biconvex, umbilicate, periph- 

 ery rounded to slightly angular; chambers spherical, 

 hemispherical, radial elongate or rarely angular in the 

 later portion; sutures radial to slightly curved on the 

 spiral side, radial on the umbilical side, depressed 

 throughout; wall calcareous, perforate, radial in struc- 

 tiu-e, siu-face tj'pically rugose with numerous large 

 pustles which may coalesce into distinct ridges, radi- 

 ating from the midpoint of each chamber on the 

 periphery, or much produced peripherally into spine- 

 like extensions, more rarely smooth; primary apertures 

 interiomarginal, umbilical, in well preserved specimens 

 covered by tegilla perforated by the accessory infra- 

 laminal and intralaminal apertures; these are the only 

 openings to the exterior. The tegilla, however, as a 

 rule are partially or wholly broken out in preservation. 



Remarks: Rugoglobigerina resembles Globotruncana 

 Cushman in the apertural characters and the presence 

 of the umbilical tegilla, but differs in the prominent 

 sirrface ornamentation and less angular chambers. 

 Rugoglobigerina may be regarded as the form ancestral 

 to Globotruncana, and various species of the latter genus 

 seem to have branched off from the main Rugoglobi- 

 gerina-stem at different geologic times. 



Rugoglobigerina differs from Globigerina d'Orbigny in 

 having the umbilical tegilla covering the primary aper- 

 ture, in having the infralaminal and intralaminal ac- 

 cessory apertures, and often in the characteristic rugose 

 and highly ornamented surface. 



In her original description of the type species, Plum- 

 mer (1926, p. 39) compared it with Globigerina rosetta 

 \= Globotruncana] stating that the umbilical features 

 were precisely the same. No orbuhnids show these 

 umbilical tegilla, but they are characteristic of Globo- 

 truncana. 



Bronnimann originally defined Rugoglobigerina with 

 three subgenera: Rugoglobigerina, s. s., Plummerella 

 (later Plummerita, new name, as Plummerella was a 

 homonym), and Trinilella. 



Plummerita was separated from Rugoglobigerina, s. s., 

 because of its peripheral spinelike chamber extensions 

 and more flattened spire, but specimens figured by 

 Bronnimann as Rugoglobigerina reicheli reicheli (1952b, 

 p. 19, text fig. 4a, b) show two definitely radial-elongate 

 chambers, and others placed in Plummerella hantkeni- 

 noides infiata show chambers as well rounded as those of 

 typical Rugoglobigerina (Bronnimann, 1952b, pi. 41, 

 text fig. 19a,b). 



