circular.) The ends of the feet are sometimes strongly convergent. The vaultings of the three swellings and the reticulation are also variable; the whole form is often irregular.
Dimensions.—Length of the three joints, a 0.02, b 0.06, c 0.04; breadth, a 0.025, b 0.1, c 0.1.
Habitat.—Cosmopolitan; Atlantic, Pacific; many stations, surface.
Subgenus 2. Pterocanidium, Haeckel.
Definition.—Free basal edge of the abdomen between the three feet convex, forming three rounded or semicircular prominent lobes between them.
11. Pterocanium eucolpum, n. sp. (Pl. 73, fig. 4).
Shell about triangular-prismatic, with two deep strictures, smooth. Length of the three joints = 1 : 3 : 3, breadth = 1 : 3 : 4. Cephalis subspherical, with a conical, oblique horn of the same length. Thorax inflated, with three hemispherical swellings between the three crests, and with subregular, hexagonal pores. Abdomen longer, with much smaller, irregular, roundish pores, forming three broad, convex lobes between the three feet. (In the figured specimen the lobes were not fully developed, and extremely thin below the line parallel to the edge. In another specimen, found afterwards in the same locality, the three lobes were much larger, semicircular, and reached almost to the basal plane of the ends of the feet by reason of their convexity.) Feet strong, with slightly convex back, divergent.
Dimensions.—Length of the three joints, a 0.03, b 0.09, c 0.1; breadth, a 0.03, b 0.09, c 0.12.
Habitat.—North Pacific, Station 244, depth 2900 fathoms.
12. Pterocanium bicorne, n. sp. (Pl. 73, fig. 5).
Shell nearly three-sided pyramidal, slender, smooth. Length of the three joints = 1 : 2 : 2, breadth = 1 : 4 : 4. Cephalis hemispherical, with two oblique, conical horns of nearly equal length. Thorax nearly hemispherical, with slightly prominent crests, and with subregular, hexagonal pores. Abdomen of about the same length, with much smaller, irregular, roundish pores, forming three convex, nearly circular lobes between the three large divergent feet. These are slender, three-sided pyramidal, longer than the shell, fenestrated at the thickened base, with some rows of larger pores; their back is slightly concave.
Dimensions.—Length of the three joints, a 0.02, b 0.04, c 0.04; breadth, a 0.02, b 0.08, c 0.09.
Habitat.—South Pacific, Station 295, depth 1500 fathoms.
