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UNITED STATES NATIONAL MUSEUM BULLETIN 215 



genera the same side might be termed either dorsal 

 or ventral, depending on whether the writer believes 

 the position of the aperture, the position of the test in 

 life, or the visibility of the early whorls to be the most 

 important basis for defining dorsal and ventral. Brotzen 

 (1942, p. 7) therefore, discarded the use of dorsal and 

 ventral and instead used the terms spiral side and 

 umbilical side. 



Thus the terminology used by various authors in 

 discussing the morphology is not always uniform, and 

 in some cases the terms used are not sufficiently expHcit. 

 A lack of concise and explicit terminology requires 

 lengthy and repetitious explanations with every 

 description. 



For these reasons certain terms previously used are 

 here adapted, others are used in a more restricted sense, 

 and some new terms are defined for structures which 

 previously have required the repetitious use of long 

 descriptive phrases for lack of a single concise and 

 expUcit term. As only planktonic Foraminifera are 

 here discussed only the terminology used for these 

 genera is given. Examples representative of each term 

 are given, as well as appropriate sketches. 



Shape and Form of Test 



Umbilicate 



Those tests with an open or closed imibilicus (the 

 point on the axis of coiling where the septa of the final 

 whorl join in an enrolled foraminifer) on one or both 

 sides of the test (text-fig. 2). 



Planispieal biumbilicate: Tests symmetrically 

 coiled, both sides lunbilicate, e. g., Hantkenina. 

 (This does not include low trochospiral forms 

 although the term has been so used in the past.) 

 Evolute. All whorls partially or wholly visible on 



both sides, but equal on the two sides, e. g., 



Hastigerina aequilatercdis (Brady). 

 Involute. Only the final whorl is visible on each 



side, e. g., Hastigerina murrayi Thomson. 



Tkochospiral: Asymmetrical tests with aU cham- 

 bers visible on one side (here termed spiral side, 

 following Brotzen) and only those of the last formed 

 whorl visible around the umbilicus on the opposite 

 (umbilical) side. 



Biconvex 

 Trochospiral 



Spiroconvex 

 Trochospiral 



Umbilico-convcx 

 Trochospiral 



Evolute Planispiral 



Involute Planispiral 



Streptospiral Enrolled Biserial 



Figure 2. — Test shapes in planktonic Foraminifera. 



Globular 



