Cushman (1930: 25) originally described Elphidium advenum var. margaritaceum as a “northern variety of the more tropical” species Elphidium advenum(Cushman 1922); thus, the type description for this species is a brief sentence describing the features that differentiate it from E. advenum: “Variety differing from the typical mainly in the character of the wall which in the variety is pearly and coarsely perforate, giving a very distinctive appearance to the test.”
This brief description of E. advenum var. margaritaceum was preceded by the following, more detailed description of Elphidium advenum: “Test of medium size for this genus, strongly compressed, periphery acute, with a narrow carina, somewhat lobulated, sides nearly parallel in peripheral view, umbilical regions depressed, often with a small central boss of clear shell material but in peripheral view not projecting beyond the contour of the test; chambers distinct, 10 to 15 in the last-formed coil, slightly inflated, especially in the last-formed portion; sutures depressed, marked by the retral processes which are short, about one-fourth the width of the chamber, 12 to 15 in number; wall smooth, translucent, finely and distinctly perforate; aperture composed of a series of small rounded pores at the base of the apertural face.”
The holotype of Elphidium advenum var. margaritaceum (USNM CC 10227) was collected from a beach at Newport, RI (Cushman 1930). More detailed locality information is not available.
The holotype and paratype of Elphidium advenum var. margaritaceum Cushman, 1930 are deposited in the Cushman Collection of Foraminifera, National Museum of Natural History, Smithsonian Institution, Washington, DC. The catalogue numbers of the holotype and paratype are USNM CC 10227 and USNM CC 18837, respectively.
The holotype was originally illustrated in Cushman (1930: Plate 10, figs. 3 a,b), and later refigured with more detailed illustrations by Lawrence Isham in Buzas et al. (1985: Figures 7.7 & 7.8). Photomicrographs of the holotype of E. margaritaceum can be accessed by searching the Smithsonian’s online collections catalogue at: http://collections.si.edu/search/index.htm.
