7. Cannobotrys pentacanna, n. sp.

Cephalis quinquelobate, with five cylindrical slender curved tubes, three of which are placed in the sagittal plane (a superior apical, a posterior caudal, and an anterior sternal), whilst the other two are paired and diverge laterally (two pectoral tubes). The five tubes correspond exactly to the five typical spines of Stephanium (p. [952]). The helmet-shaped occipital lobe of the shell is twice as large as each of the two anterior frontal lobes, and three times as large as each of the two lateral buccal lobes. Pores numerous.

Dimensions.—Length of the shell 0.07, basal breadth 0.04.

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

Family LVII. Lithobotryida, n. fam.

Definition.—Botryodea dithalamia, the shell of which is composed of a lobate cephalis and a simple thorax, without abdomen.

The family Lithobotryida comprises those Botryodea in which the shell is divided by a transverse annular constriction into a lobate cephalis and a simple thorax. They correspond therefore to the Dicyrtida among the Cyrtoidea, and to the Phormospyrida among the Spyroidea. The thorax, or the second shell-joint, is in all these three families a secondary production, arising from the base of the cephalis; therefore the Lithobotryida must be phylogenetically derived from the Cannobotryida.

Several species of Lithobotrys were first described by Ehrenberg as Lithobotrys and Lithocorythium. These two genera are, however, identical, as has been demonstrated by Bütschli (1882, loc. cit., p. 519). Some other species united by Ehrenberg with Lithobotrys belong to other genera. The number of Lithobotryida found in the "Radiolarian ooze" of the Challenger collection, is far greater than that of the Cannobotryida and Pylobotryida. But only a small part of them could be thoroughly examined and described here, so that their number may be greatly augmented by further accurate researches. We here arrange those forms in four genera, representing two different subfamilies. The terminal mouth of the thorax remains open in the Botryopylida, whilst it becomes closed by a lattice-plate in the Botryocellida. In each group there are shells with and without porous tubes. The number of these tubes, and also the number of lobes of the cephalis, is very variable, and may in future serve for the distinction of more genera.

Synopsis of the Genera of Lithobotryida.

I. Subfamily Botryopylida.

Mouth of the thorax open.

Cephalis without porous tubes,488. Botryopyle.
Cephalis with a variable number of porous tubes,489. Acrobotrys.

II. Subfamily Botryocellida.

Mouth of the thorax closed by a lattice-plate.

Cephalis without porous tubes,490. Botryocella.
Cephalis with a variable number of porous tubes,491. Lithobotrys.