1460 THE VOYAGE OF H.M.S. CHALLENGER. 



a corona of spines. It corresponds to Calocyclas among the Tricyrtida and Anthocyrtis 

 among the Dicyrtida. 



Subgenus 1. Cyrto])horinium, Haeckel. 



Definition. — Shell with six (sometimes five or seven) feet on the peristome 

 (three perradial alternate with three interradial). 



1. Cyrtojihormis armata, n. sp. (PL 78, fig. 17). 



Shell spiny, spindle-shaped, with three annular septa. Length of the four joints = 3 : 4 : 5 : 6. 

 The third joint is the broadest, being twice as broad as the constricted mouth. Pores irregular, 

 roundish. Cephalis conical, armed with a bunch of strong, conical spines, and distinguished by 

 double-contoured pores. Peristome with six (sometimes five or seven) triangular, vertical, parallel, 

 or shghtly divergent feet. 



dimensions. — Length of the shell (with four joints) 018, breadth O'OQ. Length of the single 

 jomts, a 0-03, b 0-04, c 0-05, d 0-06. 



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



2. Cyrtophormis ovata, n. sp. 



Shell rough, ovate, very thick-walled, witli three distinct strictures. Length of the four 

 joints = 1 : 1 : 2 : 3. The fourth joint is the broadest, inversely hemispherical, and tliree times as 

 broad as the constricted mouth. Pores regular, circular, hexagonaUy framed. Cepliahs hemi- 

 spherical, with a pyramidal horn of the same lengtli. Peristome with a coronal of six short, 

 conical, curved, outwardly convex teeth. 



Dimensions. — Length of the shell (with four joints) 0'2, breadtli 014. Lengtli of the single 

 jomts, a 0-02, b O'OS, c 0-06, d OW. 



Habitat. — Western Tropical Pacific, Station 225, depth 4475 fathoms. 



Subgenus 2. Cyrtophormiscus, Haeckel. 



Definition. — Shell with nine (sometimes eight or ten) feet on the peristome 

 (three perradial alternate with six interradial). 



3. Cyrtophormis cingulata, n. sp. (PI. 78, fig. 18). 



Shell spiny, spindle-shaped, with three internal annular septa, and three external girdles of 

 spines. The second and third joints are of nearly equal length, twice as broad as tlie first, and 

 half as broad as the fourth joint. The third joint is the broadest, and twice as broad as the con- 

 stricted mouth. Pores subregular, chcular. Cephalis hemispherical, with a large apical horn, and 



