Subfamily 3. Spongolarcida, Haeckel

Definition.—Larcarida with spongy lentelliptical shell (with or without enclosed medullary shell).

Genus 270. Spongolarcus, n. gen.

Definition.—Larcarida with lentelliptical spongy shell, containing a central cavity of the same form, without medullary shell (without radial spines).

The genus Spongolarcus differs from Cenolarcus (its probable ancestral form) only in the development of spongy framework forming the wall of the hollow lentelliptical shell. It corresponds, therefore, to Plegmosphæra among the Sphæroidea, and to Spongellipsis among the Prunoidea. From these two similar spongy Sphærellaria it differs in its characteristic lentelliptical form, with three dimensive axes of unequal length.

1. Spongolarcus lentellipsis, n. sp.

Spongy network of the shell very loose, its meshes fifteen to twenty times as broad as the bars. Surface of the shell nearly smooth; diameter of its internal cavity twice as large as the thickness of its wall. Proportion of the three dimensive axes = 2 : 3 : 4.

Dimensions.—Length 0.16, breadth 0.12, height 0.08; thickness of the spongy wall 0.05.

Habitat.—Pacific, central area, Station 274, surface.

2. Spongolarcus triaxonius, n. sp.

Spongy network of the shell rather loose, its meshes twelve to sixteen times as broad as the bars. Surface of the shell rough; diameter of its internal cavity about eight times as large as the thickness of its wall. Proportion of the three dimensive axes = 2 : 2.5 : 3.

Dimensions.—Length 0.25, breadth 0.2, height 0.16; thickness of the spongy wall 0.025.

Habitat.—North Pacific, Station 253, surface.

3. Spongolarcus dimensivus, n. sp.

Spongy network of the shell dense, its meshes four to eight times as broad as the bars. Surface of the shell thorny; diameter of its internal cavity about fifteen times as large as the thickness of its wall. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Length 0.2, breadth 0.16, height 0.12; thickness of the spongy wall 0.01.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

4. Spongolarcus amphicentria, Haeckel.

? Amphicentria salpa, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 296; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. ii. fig. 18.

? Spongurus salpa, Haeckel, 1862, Monogr. d. Radiol., p. 466.

Spongy network of the shell compact, its meshes about the same breadth as the bars. Surface of the shell spiny, with some larger spines around the poles of the axis; diameter of the internal cavity about six times as large as the thickness of its wall. Proportion of the three dimensive axes = 1 : 2 : 3. (Perhaps this Spongolarcus is identical with Amphicentria salpa, very imperfectly described and figured by Ehrenberg, loc. cit.?)

Dimensions.—Length 0.14, breadth 0.09, height 0.05; thickness of the spongy wall 0.015.

Habitat.—North Atlantic; off Greenland, 1000 fathoms, Ehrenberg; Station 64, depth (2700) fathoms.

Genus 271. Stypolarcus, n. gen.

Definition.—Larcarida with lentelliptical spongy shell, composed of compact spongy framework, without central cavity and medullary shell (without radial spines).

The genus Stypolarcus differs from Spongolarcus in the absence of any central cavity. This is quite filled up by spongy framework, which forms the whole mass of the lentelliptical body. Stypolarcus bears therefore the same relation to Spongolarcus that Styptosphæra does to Plegmosphæra.

1. Stypolarcus spongiosus, n. sp.

Lentelliptical shell composed in the whole mass of loose, spongy framework of similar texture, with irregular meshes, about ten to twenty times as broad as the thin bars. Surface rough, without radial spines. Proportion of the three axes = 3 : 4 : 5.

Dimensions.—Length 0.2, breadth 0.16, height 0.12.

Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.