Page:Scientific results HMS Challenger vol 18 part 1.djvu/901

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Definition.—Spiral convolutions of the cortical shell double.

4. Spirema diplospira, n. sp.

Cortical shell lentelliptical, with smooth surface; proportion of its three dimensive axes = 6 : 7 : 8. In the median plane are visible three perfect turnings of a double spiral, the breadth of which gradually increases; the broadest (third) convolution three times as broad as the simple lentelliptical medullary shell.

Dimensions.—Length of the shell 0.24, breadth 0.21, height 0.18; medullary shell 0.02.

Habitat.—Tropical Pacific, Philippines, Station 200, depth 250 fathoms.

5. Spirema subglobosum, n. sp.

Cortical shell nearly spherical, with thorny surface; proportion of its three axes = 2 : 2.1 : 2.2. In the median plane are visible two perfect turnings of a double spiral, the breadth of which in the second convolution is four times as great as that of the first convolution and the simple spherical medullary shell.

Dimensions.—Length of the shell 0.22, breadth 0.21, height 0.2; medullary shell 0.02.

Habitat.—Tropical Atlantic, off Sierra Leone, Station 348, depth (2450) fathoms.

Definition.— with simple, spherical or subspherical, medullary shell, and lentelliptical or subspherical, spirally constructed cortical shell; surface covered with numerous, simple or branched, radial spines.

The genus Lithelius, founded by me in 1862, and represented by two Mediterranean species, was at that time the only known form of this family, which now contains six genera and twenty-seven species. It differs from the foregoing Spirema in the possession of numerous radial spines on the surface. These may be either simple or branched. The spiral may be simple or double, and according to this latter modification we distinguish two different subgenera.

Definition.—Spiral convolutions of the cortical shell simple.

1. Lithelius spiralis, Haeckel.

Lithelius spiralis, Haeckel, 1862, Monogr. d. Radiol., p. 519, Taf. xxvii. figs. 6, 7.

Cortical shell lentelliptical, one and a third times as long as broad, covered with very numerous (one hundred to one hundred and fifty or more) simple, bristle-shaped radial spines, about as long