122 



P. BRONNIMANN AND J.E. WHITTAKER 



triserial, consisting of large subglobular chambers, somewhat 

 compressed in axial direction, making up major part of the 

 test. Coiling tight and axial depression (umbilicus) closed. 

 Sutures well defined. Single interiomarginal aperture a small 

 arch resting with its slightly upturned border completely on 

 surface of first chamber of final whorl. Agglutinant rather 

 coarse. 



Dimensions (holotype). Height of test — 160 urn; width 

 (umbilical diameter) — 150 |i,m. 



Remarks. Millett (op.cit., pi. 5,, figs 10a, b) attributed this 

 small, rather fragile, conical form, to Haplophragmoides 

 anceps Brady. The aperture is a broadly rounded interiomar- 

 ginal arch, sitting with its border completely on the final 

 whorl and therefore the species should belong to Trocham- 

 mina (see Bronnimann et al., 1983). Fig. 23 illustrates a 

 typical specimen from the Millett Collection but there are 

 extremes (Paratype BMNH no. 1955.11.1.1088; Fig. 24) 

 where the height of the trochospire and the umbilical diam- 

 eter are about the same or the former even appears to be 

 slightly larger. In 1983, Bronnimann et al. held great store by 

 the fact that in the Trochamminacea the umbilical diameter 

 was invariably greater than the length of the axis of coiling 

 (height of the trochospire), whereas in the Ataxophragmia- 

 cea the reverse was true. This is the first time we have found a 

 species, and apparently a single population, at the borderline 

 of the two groups. For this reason we have only tentatively 

 placed this interesting species in Trochammina. 



The true H. anceps Brady, 1884 is the type species of 

 Globotextularia Eimer & Fickert, 1899. This is a robust, deep 

 water form, much larger than Millett's species, with a very 

 high, often irregular coil, an open umbilicus and larger 

 aperture. 



Environment. According to Millett (1899: 361), . . . 'speci- 

 mens [of "H. anceps'] are numerous and well distributed'. 

 They are found at stations 5,11,12 (Area 1) and 27,28 (Area 

 2). It is associated with the agglutinating foraminifera Ammo- 

 baculites exiguus at stations 12 and 27 and rare Acupeina 

 triperforatai ' Arenoparrella mexicana at Station 5. The former 

 is found in both marginal marine and brackish localities, 

 whereas the latter are true brackish forms. It is therefore not 

 known for certain whether T. ? milletti is a marine or a 

 brackish species. 



Genus TRUNCULOCAVUS gen.nov. 



Type species. Trunculocavus durrandi sp.nov. 



Diagnosis. Test free, initially biserial, then abruptly unise- 

 rial. Biserial chambers subglobular, uniserial chambers with 

 circular transverse section. Wall agglutinated, of 

 Trochamminina-type. Aperture single, terminal, circular and 

 large, devoid of everted border. 



Name. Derived from the Latin: cavus, a hole or hollow, and 

 trunculus, tip or end. 



Remarks. Our new genus has the basic morphology of 

 Bigenerina d'Orbigny, 1826 (type species B. nodosaria d'Or- 

 bigny, 1826), but differs in the large circular aperture of the 

 final chamber of the uniserial stage, devoid of a border 

 structure. In contrast, the terminal aperture of B. nodosaria 

 is a small central porus with everted border. According to 

 Loeblich & Tappan (1987: 172), Bigenerina also has a perfo- 



rate ('canaliculate') wall, whereas Trunculocavus has a 

 Trochamminina-type wall. 



In the Millett material, there are well-preserved specimens 

 of Trunculocavus durrandi showing an organic structure 

 within the large rounded aperture. This structure is different 

 from the inner organic sheet (inner organic lining in the sense 

 of Bender, 1989: 278), which occurs along the inside of the 

 wall of the Trochamminina, because it is independent of the 

 agglutinated-organic wall proper. It is suggested that it repre- 

 sents the epidermal layer of the protoplasmic body of the 

 foraminifer. Therefore, we must distinguish between this type 

 of organic structure, as part of the protoplast, and the inner 

 organic sheet which covers the inside of the agglutinated wall 

 of the Trochamminina-type test (see Bronnimann & Whit- 

 taker, 1988), which, although has also been produced by the 

 protoplast, is not directly part of it. 



This organic structure, or the epidermal layer of the 

 protoplasmic body, occurs inside the terminal aperture of the 

 test, either as a large rounded opening limited by a thickened 

 border (Fig. 7), or it closes the aperture of the test completely 

 and reveals 6 small perforations with tube-like extensions 

 (Fig. 1) along the apertural periphery. This organic structure 

 does not have a counterpart in the agglutinated-organic phase 

 of the wall, another reason for separating it nomenclatorally 

 from the inner organic sheet. In fossil specimens, the epider- 

 mal layer of the protoplast will naturally be absent, so it could 

 not be considered taxonomically. At present, therefore, it has 

 no standing in the systematic treatment of these agglutinated 

 foraminifera, which is based on test features alone. It should, 

 however, be remembered that this situation would have to be 

 modified once it becomes possible to take into consideration 

 the features of the living organism. 



In a paper by Petrucci et al. (1983: 72-75), there is a 

 taxonomic appendix by Medioli, Scott & Petrucci. In this 

 appendix a new species, Polysaccammina hyperhalina, is 

 introduced which is of interest here because it shows organic 

 features similar to those described for T. durrandi. P. hyper- 

 halina has a large circular terminal aperture with an irregu- 

 larly finished border, devoid of particular border structures. 

 Medioli et al. (1983: 72, pi. 21, figs 2,3,6,8) described the 

 aperture as invaginated ... 'to form an inner, backward 

 pointing funnel'. Their pi. 1, figs la, 2a show the large, 

 rounded aperture is closed on the inside, as in T. durrandi, by 

 an organic structure having in its centre a small circular porus 

 with everted border. Also, as in T. durrandi, this small 

 opening appears to be a different from the aperture of the test 

 and that it represents the epidermal layer of the protoplast, 

 with features which have no counterpart in those of the test 

 wall and which is different from the inner organic lining. 



Trunculocavus durrandi sp.nov. 



Figs 2.1,3-8 



1900 Bigenerina digitata d'Orbigny var. Millett: 6, pi. 1, 

 figs la,b (non Bigenerina (Gemmulina) digitata d'Or- 

 bigny, 1826). 



Diagnosis. As for genus; Trunculocavus is presently mono- 

 typic. 



Name. In honour if A. Durrand FRMS, the collector of the 

 Malay Archipelago foraminifera described by Millett. 



Holotype. BMNH no. 1955.11.1.187. Illustrated in Figs 

 3,4. From Station 9, Area 1. 



Description (holotype. Test free, small and elongate; ini- 



