1432 THE VOYAGE OF H.M.S. CHALLENGER. 



The genus Tricolocapsa differs from the preceding Theocapsa in the loss of the 

 apical horn, and exhiliits therefore to it the same relation that Theocamjye bears 

 to Tlieocorys. In some species (PL QQ, figs. 1, 3) a small tube begins to be 

 developed on the cephalis, and these may perhaps be separated as a pecuUar genus, 

 Tricolopera. 



Subgenus 1. Tricoloeapsula, Haeckel. 

 Definition. — Thorax of about the same size as the abdomen, or larger. 



1. Tricolocap)sa thcop>hrasti, n. sp. (PI. QQ, fig. 1). 



Shell slenderly ovate, with two slight strictures. Length of the three joints = 2:8:5, breadth 

 = 3:7:5. Cephalis hemispherical, with a larger, tube-like, cervical pore at the collar stricture. 

 Thorax very thick-walled, with irregular, roundish, double-edged pores, smaller than the bars 

 between them. Abdomen smaller, inversely campanulate-conical, with very irregular pores. 

 Basal pole acute. 



Dimensions. — Length of the three joints, a 0-02, I O'OS, c 0-05 ; breadth, a 0-03, h 0-07, c 0-05. 



Habitat. — Central Pacific, Station 271, depth 2425 fathoms. 



2. Tricolocapsa dioscoridis, n. sp. (PL QQ, fig. 3). 



Shell short and broad, with two deep strictures. Length of the three joints = 3:5:4, breadth = 

 4:7:5. Cephalis hemispherical, with a lai-ger, tube-like, cervical jjore above the collar 

 stricture. Thorax very broad, with irregular, large and spare, roundish pores. Abdomen much 

 smaller, inversely conical, with smaller pores. Basal pole obtuse. 



JDimeTisions. — Length of the three joints, a 0'03, b 0'05, c 004 ; breadth, a 0'04, b 0-07, c 0-05. 



Habitat. — Central Pacific, Station 274, depth 2750 fathoms. 



3. Tricolocapsa linncei, n. sp. (PL QQ, fig. 5). 



Shell short and broad, with two deep strictures. Length of the three joints =1:4:2, breadth 

 = 1:4:2. Cephalis hemispherical. Thorax thick-walled, inflated, with subregular, circular, double- 

 edged pores. Abdomen much smaller, thin-walled, with irregular, polygonal pores. Basal pole 

 hemispherical, rounded. 



Dimensions. — Length of the three joints, a 0'02, h 0'08, e 0'05 ; breadth, a G'03, b 0'08, c 0'05. 



Habitat. — South Pacific, Station 295, depth 1500 fathoms. 



