S53

Didymocyrtis tetrathalamus coronatus (Haeckel)

Cyphinidium coronatum Haeckel, 1887, p. 372.

Panartus tetrathalamus coronatus Haeckel, Nigrini, 1970, p. 168, pl. 1, figs. 13, 14

DESCRIPTION "This subspecies is identical in all respects to P. tetrathalamus tetrathalamus, except for the development of a corona of stout, unbranched, 3-bladed spines on the distal ends of the cortical twin-shell and/or on the polar caps. When polar caps are present, the spines commonly extend without interruption beyond the point of junction with the cap. There may be as many as 9 or 10 spines on each end of the cortical twin-shell which is, in general, smaller than that of P. tetrathalamus tetrathalamus." (from Nigrini, 1970).

DIMENSIONS "(based on 20 specimens). Length of cortical twin-shell 96 to 119 microns. Maximum breadth of cortical twin-shell 64 to 88 microns. Maximum length of polar spines 56 microns." (from Nigrini, 1970).

Plate 6, figures 2a,b

S54

RECENT DISTRIBUTION

1. Nigrini, 1970, fig. 12; belongs to a transitional assemblage derived by recurrent group analysis of North Pacific samples.

2. Sachs (1973), Moore (1974), Molina-Cruz (1975) and Robertson (1975) all combined this species with O. tetrathalamus tetrathalamus in their counts.