1328 THE VOYAGE OF H.M.S. CHALLENGER. 



Genus. 587. Theopodium, 1 Haeckel, 1881, Prodromus, p. 435. 



Definition. T heopilida (vel Tricyrtida triradiata aperta) with three divergent 

 solid ribs, which lie in the wall of the thorax and the abdomen, and are prolonged 

 into three solid terminal feet. 



The genus Theopodium and the following closely allied Pterocanium differ from 

 the preceding four genera in the development of the three radial rods or the primary 

 cortinar spines, which are not free lateral wings, but longitudinal ribs enclosed in the 

 wall of the thorax and abdomen, and prolonged over the basal mouth into three 

 free terminal feet. These are solid in TJieopodiiim, which, therefore, corresponds to 

 Lychnocanium among the Dicyrtida. 



1. TJieopodium tricostatum, n. sp. (PI. 97, fig. 14). 



Shell three-sided pyramidal, thorny, with two distinct strictures. Length of the three 

 joints = 1:2:2, breadth = 1:3:4. Cephalis hemispherical, with a stout conical horn of the same 

 length. Thorax with regular, circular, hexagonally-framed pores. Abdomen with irregular, 

 roundish pores of very different sizes. From the middle part of the thorax arise the three 

 prominent, wing-like edges of the pyramid, which are prolonged over its wide mouth into three 

 stout, pyramidal, divergent feet about as long as the thorax, with dentate, lamellar edges. 



Dimensions. Length of the three joints, a 0'02, 6 0'07, c 0'06 ; breadth, a 0'04, & O09, c 012. 



Habitat. Tropical Atlantic, Station 347, depth 2250 fathoms. 



2. Theopodium, pyramidale, n. sp. 



Shell three-sided pyramidal, rough, without external strictures, but with two broad internal 

 girdles. Length of the three joints = 1:2:6, breadth = 2:4:8. Cephalis with a thick horn of 

 the same length, conical. Thorax with very small, regular, circular pores. Abdomen with 

 irregular, roundish pores of very different sizes. From the collar stricture arise the three recti- 

 linear edges of the pyramid, which are prolonged over its wide-open mouth into three stout, 

 divergent, pyramidal feet, about as long as the thorax. 



Dimensions. Length of the three joints, a 0'02, & 0'04, c 012 ; breadth, a 0'04, & 0'075, c 015. 



Habitat. Fossil in Barbados. 



Genus 588. Pterocanium^ Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. 



Wiss. Berlin, p. 54. 



Definition. T heopilida (vel Tricyrtida triradiata aperta) with three divergent 

 ribs, which run along the thorax and abdomen, and are prolonged into three latticed 

 terminal feet. 



1 Theopodium = Divine foot ; iio;, is-itiiov. 



2 Pterocanium = Basket with wings ; TTSJO'I/, nation. 



