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Actinomma popofskii (Petrushevskaya, 1967)

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Echinomma popofskii
Massive shell consists of three spheres. Innermost small irregular shape. Intermediate thin-walled, with 8-9 pores on half equator; from it project (Figure 12,1) slender triagonal needles uniting it to outer sphere. Outer sphere not of exactly regular shape (Figure 12, II), has 13-15 round pores on half equator. Walls of outer sphere thick, pores often with hexagonal frames. Very slender additional spinules arising from surface of outer sphere (Figure 12, III). Additional 11-14 powerful faceted radial needles usually broken off. It is interesting that these needles are not extensions of those connecting intermediate to outer sphere but arise independently of them (Figure 12, II) on surface of third sphere. This means of connection between intermediate and outer sphere differentiates described species from foregoing and from other known species of genus Echinomma. Therefore, we consider it possible to describe it as a new species and designate it in memory of A. Popovski Echinomma popofskii.
Dimensions: diameter of innermost sphere 18-25μ, diameter of intermediate sphere 45-50μ, diameter of outer sphere 110-130μ, length of additional spicules up to 25μ, thickness of basic radi al needles at base 20- 22μ.
Location. In our materi al the species was detected in samples of deepwater sediments, where shells of E. popofskii constitute less than 1% of total number of shells. This species was encountered both south and north of zone of Antarctic convergence in Indian and Pacific Ocean sectors.
Holotype in the collection of the Zoological Institute of AN SSSR (ZIN) on preparation No. 1 of station 220 of the "Ob' . "
Note. This species i s very si milar in all features to E. quadrisphaera found by Dogel' in 1954, but differs from it in its somewhat smaller dimensions and more regularly spherical outer shell (in E. quadrisphaera the depressions and eminences that are smoothed over in our species are present). In addition, E. quadrisphaera often develops a fourth sphere outside the third. Typical specimens of E. quadrisphaera are encountered in our material in sediments of the temperate and tropical zones.
Petrushevskaya 1967


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