Page:Scientific results HMS Challenger vol 18 part 1.djvu/549

Rh

Definition.— with a spongy ellipsoidal or cylindrical shell, without an internal latticed medullary shell.

Definition.— with an ellipsoidal or cylindrical spongy shell, containing an internal cavity, without a latticed medullary shell. Polar spines absent.

The genus Spongellipsis embraces those very simple Spongurida in which the ellipsoidal central capsule is enclosed in a spongy cortical shell of the same form. It corresponds, therefore, to Plegmosphæra among the, to Plegmodiscus among the , and to Spongolarcus among the. In some species the ellipsoidal form is prolonged and passes into a cylindrical one.

Definition.—Surface of the shell smooth or rough, without radial spines.