1332 THE VOYAGE OF H.M.S. CHALLENGER. 



circular.) The euds 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 01, c Ol. 



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 semicircuhxr prominent lobes between them. 



11. Pterocanium eucolpum, n. sp. (PI. 73, fig. 4). 



Dietyopodium eucolpum, Haeckel, 1881, Prodromus et Atlas. 



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 high 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 D'OO, c 01 ; breadth, a 0-03, b 0-09, c 012. 



Habitat. — North Pacific, Station 244, depth 2900 fatlioms. 



12. Pterocanitiin hicornc, n. sp. (PI. 73, fig. 5). 



Didyo-podimn hicorne, Haeckel, 1881, Prodromus ot Atlas. 



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 l.iase, with some rows of larger pores ; 

 their back is slightly concave. 



Dimensions. — Length of the three joints, a 002, b 0-04, c 0-04 ; breadth, a 0-02, b 0-08, c 0-09. 



Habitat. — South Pacific, Station 29o, depth 1500 fathoms. 



