. Annual report. New York State Museum; Science; Science. SOME NEW DEVONIC FOSSILS 233 Nuculana (Ditichia) securis nov. Cf. Nuculana securiformis Goldfuss (sp.) Petrefacta Ger- maniae. 2: 151, pi. 124, fig. 8 and Beushausen, Devon. Aviculiden Deutschlands, p. 59, pi. 4, fig. 26-28 Shell small, transversely elongated and snouted, beak approxi- mately median, hinge line sloping slightly in front, deeply incurved behind. Posterior extensions narrow, curved gently upward at the extremity, anterior extremity broad and blunt; umbones not promi- nent, umbonal ridge obscure; greatest convexity of the
. Annual report. New York State Museum; Science; Science. SOME NEW DEVONIC FOSSILS 233 Nuculana (Ditichia) securis nov. Cf. Nuculana securiformis Goldfuss (sp.) Petrefacta Ger- maniae. 2: 151, pi. 124, fig. 8 and Beushausen, Devon. Aviculiden Deutschlands, p. 59, pi. 4, fig. 26-28 Shell small, transversely elongated and snouted, beak approxi- mately median, hinge line sloping slightly in front, deeply incurved behind. Posterior extensions narrow, curved gently upward at the extremity, anterior extremity broad and blunt; umbones not promi- nent, umbonal ridge obscure; greatest convexity of the valve anterior near the hinge; surface generally convex over the body of the shell, depressed toward the posterior extremity; hinge toothed almost to the extremity of the posterior extension, while the marginal surface along the extension is excavated and slightly ridged. Just within the position of the muscle scars which are usually faint are two faint shell ridges or clavicles preserved as grooves on the sculpture. 4^ Nuculana (Ditichia) securis casts. Of these the anterior is the larger, both are broad and low, but the structure is altogether unusual though not unexpected in this genus. This structure is expressed in Nuculites by the strong development of an anterior ridge and in such forms occasionally the two ridges appear as in the species N. (Cu cull el la) e 11 i p t i c a Maurer of the Coblentzian for which Sandberger proposed the generic term Ditichia because of this structure. Beushausen however considers this development of a second ridge of only specific value and embraces such species within Cucullella. For the same reason we may hold the present species within the genus Nuculana though shells of this lediform type have not before shown such structures. The presence of these muscular clavicles is the only apparent difference between this shell and the Nucu- lana securiformis Goldfuss of the Coblentzian. The surface of the valves is covered with very fine concentri
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