N31

Plectopyramis dodecomma Haeckel

Plectopyramis dodecomma Haeckel, 1887, p. 1258, pl. 54, fig. 6; Benson, 1966, p. 424, pl. 29, fig. 3

DESCRIPTION

"Test consisting of a small sub-hemispherical, poreless cephalis, with or without apical horn or spine, and smooth, long, conical thorax, broad at the base, consisting of 8-11 heavy, longitudinal bars or ribs, circular in section, and joined by transverse bars, likewise circular in section, that are continuous around the circumference, straight not curved between adjacent longitudinal ribs. Thoracic pores subrectangular, increasing in size toward the base; in the proximal one third of the thorax the pores are either infilled by silica or by a thin, reticulate, secondary meshwork. Collar pores not observed in all tests, but at least three are present and four if vertical bar is developed. Apical spine variable from absent, to a short spine, to a heavy, conical horn either straight or curved. Vertical spine not observed but may be present in some specimens. One specimen observed with a raised thoracic rib corresponding to one of the primary basal spines and extending for about one-third the length of the thorax...

"This species differs from Peripyramis circumtexta Haeckel in the absence of branched spines arising from the thorax and in the presence of transverse bars that are continuous around the circumference." (from Benson, 1966).

DIMENSIONS "maximum length of test 160-277 mu; maximum breadth of thorax 117-178 mu; length of cephalic 10-16 mu breadth of cephalis 11-17 mu; length of apical spine or horn 0-37 mu." (from Benson, 1966).

REMARKS

1. For further synonymy see Benson (1966).

Plate 21, figure 5

N32

RECENT DISTRIBUTION

1. Benson, 1966; "very rare in the Gulf [of California] but occurs as far north as station 184. It is relatively more abundant in the southern Gulf."

2. Molina-Cruz, 1975, Code N23; counted together with Peripyramis circumtexta Haeckel, but not used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent N23 at each station.