Genus Helicostegina Barker and Grimsdale, 1935 Helicostegina soldadensis Grimsdale, n. sp. (Plate 46, figures 1–7) The upper Eocene orbitoid-bearing rocks of Trinidad and Soldado Island contain abundant specimens of a small new species of Helicostegina; this species is of considerable interest in that it forms a link between Helicostegina gyralis Barker and Grimsdale, and the genus Helicolepidina Tobler. In its characters it is completely transitional and could readily find a place in either genus; and its relegation to Helicostegina rather than to Helicolepidina is justified by a desire to avoid the slight emendation of the latter genus necessary to allow its reception therein (see Vaughan, 1933d, p. 298, and Barker, 1934, p. 345), and to express a certain symmetry in the evolutionary picture: The above “tree” is modified from the one previously published (Barker and Grimsdale, 1936, Jour. Paleont., vol. 10, p. 244), to include this new species. In other words, Helicostegina soldadensis completes the evidence for the descent of Helicolepidina, to which genus it stands in a relation similar to that between Helicostegina dimorpha and Eulinderina. The description of the species is as follows: Test small, stoutly lenticular, with a wide flange one chamber thick, frequently broken. The ornament consists of irregularly-developed, wavy, radiating costae, with a variable number of papillae upon the central umbonate area. The central part consists of an involute, almost planispiral coil, acutely bordered; the outer wall is thick and pierced by numerous cribriform perforations. The chambers of the spire are separated from each . . .