1448 THE VOYAGE OF H.M.S. CHALLENGER. 



The genus Stichopera, and the two following genera, represent the small subfamily 

 of Stichoperida, or those triradiate Stichocyrtida in which the terminal mouth is closed 

 by lattice-work. In Stichopera the three radial appendages are either solid lateral ribs 

 or longitudinal combs of spines ; the closed basal part of the shell is rounded, not 

 pointed. It may be derived either from Stichopilium by closure of the mouth, or from 

 Lithornithium by increase of the number of the joints. 



Subgenus 1. Stichoperina, Haeckel. 

 Definition. Shell with three solid radial ribs, or longitudinal dentate crests. 



1. Stichopera ovata, n. sp. 



Shell ovate, with three distinct strictures. Length of the four joints = 2:3:4:6. The fourth 

 joint is the broadest, and twice as long as the second, with hemispherical basal pole. Cephalis 

 hemispherical, with a conical horn of twice the length. Along the second and third joints descend 

 three prominent divergent ribs, which disappear in the middle zone of the fourth joint. Pores 

 regular, circular. 



Dimensions. Length of the shell (with four joints) 015, breadth O'l. Length of the single 

 joint, a 0-02, 6 0"03, c 0'04, d 0'06. 



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



2. Stichopera lagena, n. sp. 



Shell bottle-shaped, with six sharp strictures ; the upper half is slender, conical, and composed 

 of six joints of nearly equal length, the lower half is formed only by the last subspherical joint. 

 Cephalis subspherical, with a pyramidal horn of the same length. From its base arise three 

 divergent ribs, which attain the greatest height in the fourth joint, and disappear in the sixth joint. 

 (Similar to Stichophcena ritteriana, PI. 75, fig. 12, but only with three ribs and seven joints.) Pores 

 regular, hexagonal. 



Dimensions. Length of the shell (with seven joints) 0'25. Length of each joint O02 to - 025, 

 of the last joint 012 ; breadth 014. 



Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



3. Stichopera serrata, n. sp. 



Shell bottle-shaped, with eight deep strictures. The first eight joints are little different in 

 length, and form together a slender cone, while the last joint is four times as long (half as long as 

 this cone), and subspherical. Cephalis conical, with a slender, prismatic horn of three times the 

 length. Along the whole shell arise three divergent, serrate ribs, which disappear towards the 

 hemispherical, basal pole. Pores subregular, hexagonal. 



