Definition.—Surface of the cortical shell smooth or a little rough, but without spines or fenestrated protuberances.
1. Cannartidium amphiconicum, n. sp.
Cortical shell thick walled, smooth with regular circular pores twice as broad as the bars; eight to nine on the half meridian, fifteen to sixteen on the half equator of each chamber. Polar tubes conical, with smaller pores, tapering towards the closed apex, about as long as one single chamber, at the base one-third as broad as the equatorial constriction. Both concentric medullary shells spherical. (Nearly identical with Cannartiscus amphiconiscus, Pl. [39], fig. 19, but differs in the possession of the double medullary shell.)
Dimensions.—Main axis of the cortical shell (without tubes) 0.15, greatest breadth 0.11; pores 0.009, bars 0.004; length of the polar tubes 0.08, basal breadth 0.04.
Habitat.—Pacific, western tropical part, Station 225, depth 4475 fathoms.
2. Cannartidium amphicanna, Haeckel.
"Curious twin Polycystin," Bury, 1862, Polycystins of Barbados, pl. xx. fig. 4.
Cortical shell thick walled, rough, with regular, circular pores, not broader than the bars; six to seven on the half meridian, ten to twelve on the half equator of each chamber. Polar tubes cylindrical, at the distal end open (broken off?), nearly as long as the main axis, about one-third as broad as the equatorial constriction. Both concentric medullary shells spherical.
Dimensions.—Main axis 0.14, greatest breadth 0.11; pores and bars 0.005; length of the polar tubes 0.13, breadth of them 0.03.
Habitat.—Fossil in the Barbados deposits.