Page:Scientific results HMS Challenger vol 18 part 2.djvu/232

1108 be advisable to distinguish a number of genera according to the different number of the porous tubes and of the lobes of the cephalis. The base of the latter is constantly closed by a basal lattice-plate, and usually exhibits two or three pairs of cortinar pores, identical with those of the Semantida.

The phylogenetic origin of the Cannobotryida may be found either in the Zygospyrida or in the Monocyrtida; they differ from these two similar groups in the lobation of the cephalis, which is effected by the development of internal septa and external constrictions.

Definition.— without tubes on the cephalis.

The genus Botryopera is the simplest form among the, the shell consisting of a lobate cephalis only, without tubes or radial appendages. It may be derived either from Dictyospyris or from Archicapsa by development of the horizontal fold in the frontal face of the shell, and the corresponding internal frontal septum, which separates the larger occipital lobe from the smaller facial half; the latter may be divided again into paired frontal lobes, lateral buccal lobes, &c. Botryopera may be the common ancestral form of many.

1. Botryopera cyrtoloba, n. sp. (Pl. 96, fig. 1).

Cephalis trilobate; the posterior odd occipital lobe helmet-shaped, about twice as large as the two paired anterior frontal lobes, which are subovate and covered by the upper half of the former. Pores small and numerous, subregular, circular; some larger pores at the base.

Dimensions.—Length of the shell 0.08, basal breadth 0.06.

Habitat.—Central Pacific, Station 265 to 274, depth 2350 to 2925 fathoms.

2. Botryopera triloba, Haeckel.

Lithobotrys triloba, Ehrenberg, 1854, Mikrogeol., Taf. xxii. fig. 30.

Cephalis trilobate; the occipital lobe subcylindrical, one and a half times as long as the two frontal lobes, which are slender, ovate and not covered by the former. Pores small and numerous.

Dimensions.—Length of the shell 0.05, breadth 0.03.

Habitat.—Fossil in Tertiary rocks of the Mediterranean (Sicily, Greece, &c.)