Abstract

Among the specimens dredged from Georges Bank in 1934 and submitted for determination was a fairly well-preserved, ramose cyclostomatous bryozoan belonging to the unusual genus Plethopora Hagenow, 1851, of the Cytisidae, species of which have hitherto been found only in the Cretaceous of Europe. In this genus the solid, cylindrical, branching zoarium consists of angular thin-walled tubes grouped in salient fascicles, or bundles, projecting at the surface in knobby elevations, or ridges, and separated by numerous nematopores, the adventitious, thread-like, angular, thin-walled, upwardly directed tubules. In the type of the genus, P. verrucosa Hagenow, from the Maestrichtian of Holland, the bundles of tubes open at the surface in elongate, rounded nodes; but in the present species the bundles are more elongate, narrow, and occasionally branched.

Plethopora americana Bassler n.sp.

(Stephenson, Plate 1, figure 18)

Description.—Zoarium cylindrical, slightly flattened, with branches 3 to 4 millimeters in diameter, dividing dichotomously at . . .

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