1154 THE VOYAGE OF H.M.S. CHALLENGER. 



1. Peridium lasanum, n. sp. 



Shell subspherical, smooth, with subregular circular pores. Basal plate with three large meshes. 

 Horn apical, vertical, of the same size and form as the three divergent smooth feet, slender pyra- 

 midal, twice to three times as long as the shell. 



Dimensions. Shell-diameter 0'06 to O07, length of the three spines 015 to 0'2. 



Habitat. North Pacific, Station 253, depth 3125 fathoms. 



2. Peridium papillatum, n. sp. 



Shell subspherical, papillate, with subregular circular pores. Basal plate with four meshes 

 (two major cardinal and two minor jugular pores). Horn occipital, oblique, three-sided pyramidal, 

 half as long as the shell and as the three widely divergent, subhorizontal, smooth feet. 



Dimensions. Shell diameter O'OY to 0'08, length of the horn 0'04, of the feet 0'08. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms. 



3. Peridium curvipes, n. sp. 



Shell hemispherical, thorny, with irregular roundish pores. Basal plate with six pores (two 

 larger middle cardinal, two smaller anterior jugular and two smaller posterior cervical pores, as in 

 PI. 53, figs. 13, 18). Horn conical, oblique, arising from the middle of the occipital face, half as 

 long as the shell. Feet slender, conical, curved, smooth, twice as long as the shell. 



Dimensions. Shell 0'04 long, 0'06 broad ; horn 0'02 long; feet 0'08 long. 



Habitat. Tropical Pacific, Station 206, depth 2100 fathoms. 



Subgenus 2. Archiperidium, Haeckel. 

 Definition. Feet spiny or branched. 



4. Peridium spinipes, n. sp. (PI. 53, fig. 9). 



Shell ovate, rough or thorny, with irregular roundish pores. Basal plate with four pores (two 

 larger cardinal and two smaller jugular pores). Horn oblique, occipital, three-sided pyramidal, half 

 as long as the shell, connected with the caudal foot by a prominent crest. Three feet horizontally 

 expanded, prismatic, spiny, about as long as the shell. 



Dimensions. Shell 0'08 long, 0'06 broad ; horn 0'04 long, feet 0'06 to 0'09 long. 



Habitat. Central Pacific, Station 266, depth 2750 fathoms. 



5. Peridium palmipes, n. sp. (PI. 53, fig. 10). 



Shell ovate, smooth, with irregular roundish pores. Basal plate with three large pores. Horn 

 oblique, three-sided pyramidal, about as long as the shell, inserted near its occipital base. Three 

 feet prismatic, slender, half as long, ending with a broad dentate plate. 



Dimensions. Shell 0'06 long, 0'05 broad ; horn 0'05 long, feet 0'03 long. 



Habitat. Western Tropical Pacific, Station 224, depth 1850 fathoms. 



