1324 THE VOYAGE OF H.M.S. CHALLENGER. 



1:10:12. Cephalis hemispherical, with six bristle-shaped spiues of half the length of the shell ; 

 three horns divergent upwards, and three alternating feet divergent downwards. Thorax nearly 

 conical. Abdomen flatter. 



Dimensions. — Length of the three joints, a 0-015, h 01, c 0-03 ; breadth, a 0-02, h O'lo, c OlS. 



Habitat. — North Pacific, Station 236, surface. 



5. Corocalyptni ludovicce, n. sp. 



Shell flatly campanulate or hat-shaped. Length of the three joints = 1:4:3, breadth = 2:7:10. 

 Cephalis hemispherical, with six bristle-shaped spines, about one-fourth to one-third as long as the 

 shell ; three horns diverging upwards, and three alternate feet diverging downwards. Thorax 

 nearly conical. Abdomen much larger than in all preceding species, inflated, with convex, lateral 

 outline; its mouth-edge curved inwards. The network is much finer than in the similar Corocalyptra 

 cmmw (PL 59, fig. 4), and the abdomen is relatively twice as long and liroad. 



Dimensions. — Length of the three joints, a 0-02, h O'OS, c 0-06 ; breadth, a 0-04, h 014, c 0-2. 



Habitat. — Central Pacific, Station 271, surface. 



C4enus 585. Dictijoccras,^ Haeckel, 18G2, Monogr. d. Radiol., p. 333 



Defiyiitio7i. — T h e o p i 1 i d a (vel Tricyrtida triradiata aperta) with three latticed 

 free lateral wings on the sides of the thorax, whi(.'h are not prolonged into the 

 cephalis. 



The genus Dictyoceras and the following Pteropilium agree with the two preceding 

 genera in the possession of three lateral wings on the sides of the thorax ; but whilst 

 these in the latter are simple solid spines, they are in the former vertical fenestrated 

 plates. Dictyocera.s may be derived from Pterocorys by development of a vertical 

 lattice-plate between the thorax and the three free lateral spines arising from it. 



1. Dictyoceras insectum, n. sp. (PI. 71, figs. G, 7). 



Shell with two distinct strictures. Length of the three joints = 1 : 3 : 2, breadth =2 : 4 : 3. 

 Cephalis hemispherical, with a slender pyramidal horn of twice the length. Thorax subspherical, 

 in the upper half with three divergent lattice-wings of the same length, each of which represents a 

 slender, fenestrated, three-sided pyramid. Abdomen subovate, with wide, truncate mouth (in the 

 figured specimen broken off). Pores circular, small, of different sizes. 



Dimensions. — Length of the three joints, a 0025, b 0-055, c 0-04 ; breadth, a 0-035, h 0-08, 

 c 0-OG. 



Habitat. — Central Pacific, Stations 263 to 274, depth 2350 to 2925 fatiioms. 



1 Dictj/oceras = Eeticulatecl liorn ; S/xn/ov, xtj«;. 



