1370 THE VOYAGE OF H.M.S. CHALLENGER. 



tudinal rows of circular, regular pores, disposed in ten to twelve transverse rows. Each pore with 

 a square, elevated frame. Mouth constricted, only one-third as broad as the thorax. 



Dimensions. Length of the three joints, a 0'02, b 0'03, c 013 ; breadth, a 0'04, b 0'06, c Oil. 



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



6. Phormocyrtis longicornis, n. sp. (PI. 69, fig. 15). 



Theocorys longicornis, Hacckel, 1881, Prodromus et Atlas, loc. cit. 



Shell slender, ovate, rough, with two slight strictures. Length of the three joints = 3:8:12, 

 breadth = 4 : 10 : 11. Cephalis hemispherical, with a very large, cylindrical horn, about as long 

 as the shell. Thorax hemispherical, with regular, circular, hexagonally-framed pores. Abdomen 

 subcylindrical, with twenty to twenty-four nearly parallel undulate ribs, and alternate longitudinal 

 rows of regular, circular pores. Mouth constricted, circular, about half as broad as the thorax. 



Dimensions. Length of the three joints, a 0'03, b 0'08, c 012 ; breadth, a 0'04, b 01, c Oil. 



Habitat. Central Pacific, Station 268, depth 2900 fathoms ; also fossil in Barbados. 



Genus 603. Alacorys, 1 Haeckel, 1881, Prodromus, p. 436. 



Definition. T heophormida (vel Tricyrtida multiradiata aperta) with numerous 

 radial ribs in the abdomen, which are prolonged over the mouth into free feet. 



The genus Alacorys and the following Cydadophora differ from the preceding two 

 genera in the formation of the radial ribs, which arise from the lumbar stricture, and lie 

 in the wall of the abdomen, but are absent on the thorax. The shell is usually large, 

 more or less pyramidal or conical, with a wide open terminal mouth. The latter is in 

 Cydadophora simply truncate, whilst in Alacorys it is surrounded by from four to 

 twelve or more terminal feet, prolongations of the abdominal ribs. According to the 

 different number of these (four, five, six, or more) some subgenera may be distinguished, 

 as Tetralacorys, Pentalacorys, Hexalacorys, &c. 



Subgenus 1. Tetralacorys, Haeckel, 1881, Prodromus, p. 436. 



Definition. Peristome armed with four feet, opposite in two meridian planes, which 

 are perpendicular to one another. 



1. Alacorys lutheri, n. sp. (PL 65, fig. 4). 



Shell papillate, with distinct collar stricture. Length of the three joints = 3:6:6, breadth = 

 3 : 8 : 10. Cephalis subpherical, with a pyramidal horn of the same length. Thorax tuberculate, 



1 A lacorys = Wing-helmet. 



