Genus Sigmomorphina

Sigmomorphina Cushman & Ozawa, 1928


Description: Chambers much compressed, triangular in section and the successive chambers added in planes of more than 180 degrees, often much twisted.



Sigmomorphina trilocularis (Bagg, 1912)


Polymorphina trilocularis Bagg, 1912, p. 75, pl. 20, figs. 15-18.

Sigmomorphina trilocularis (Bagg), Todd and Low, 1967, p. A25, pl. 3, figs. 15, 16.


Description: Test very minute and smooth, consisting of three elongated oval segments two of which are equilateral and symmetrical; the central chamber extends halfway below the base of the two side chambers. Aperture radiate, subcentral. Its greatest length is 0.75 millimeter and its breadth, 0.28 millimeter.


Remarks: This species was described from Pleistocene beds at Timms Point, San Pedro, California. Todd and Low (1967) recorded the modern species occurring around the northern Pacific, and that it varies in size with the length measuring up to 2.5 mm and breadth to 0.75 mm. These authors also noted that the test morphology is variable; some with more deeply depressed sutures and chamber arrangement giving a more twisted appearance.


Distribution: In Puget Sound, S. trilocularis is rare and was found in the northern and central part of the main passages.