S37

Anomalacantha dentata (Mast)

Heteracantha dentata Mast, 1910, p. 157, Nigrini, 1970, p. 167, pl. 1, fig. 9

Cladococcus lychnosphaera Hollande and Enjumet, 1960, p. 115, pl. 55, figs. 1, 2

Anomalacantha dentata (Mast), Benson, 1966, p. 170, pl. 5, figs. 10, 11

DESCRIPTION "Small, spherical, latticed shell from which originate 8-12 or more long, broad, regularly arranged, three-bladed radial spines, each with thorns or lateral branches originating from the blades at 2-5 or more verticals. Pores of shell circular, of equal size, 5-6 on half the shell circumference, surrounded by well defined, hexagonal frames. Surface of shell either smooth, thorny, or with thin, conical, often distally forked, secondary spines of variable length (up to 25(), all originating singly from the nodes of the intervening bars. In fully developed tests a verticel of long, arborescently branched lateral spines is present on each main spine. All verticels at a common distance from the center of the test. The lateral, arborescent branches do not anastomose with those of adjacent main spines; therefore, an outer shell is not developed." (from Benson, 1966).

DIMENSIONS "Based on 30 specimens: diameter of shell 53-69(; length of radial spines 166-246(, breadth at their bases 6-12(." (from Benson, 1966).

REMARKS

1. The generic name Anomalacantha was proposed by Loeblich and Tappan (1961) because they found the name Heteracantha to be previously occupied.

Plate 4, fiqure 4

S38

RECENT DISTRIBUTION

1. Benson, 1966 "... nearly cosmopolitan in the Gulf [of California] and undergoes a marked increase in frequency in the northern half of the Gulf."

2. Nigrini, 1970, fig. 8; "according to Benson (1966), this species is widespread in Holocene tropical seas. This was not found to be the case by the author." Belongs to a transitional assemblage derived by recurrent group analysis of North Pacific samples.

3. Sachs, 1973, Code l9S; "The species is always rare (less than 3%), and consequently is patchily distributed. It loads on the Transition (Southernmost) factor."

4. Robertson, 1975; "This species loads most heavily in factor 3 (transitional ). At the present its highest abundances are in a small region centered at 40°N and east of 155°W. It is absent north of about 46°N except for rare occurrences in three samples. At 18,000 YBP it is essentially absent north of about 40°N."