1354 THE VOYAGE OF H.M.S. CHALLENGER. 



as large as the thoracic pores. Feet nearly vertical, only slightly divergent, S-shaped, bent, as 

 long as the abdomen, cylindrical ; at the distal end shovel-shaped and fenestrated (often much 

 more than in Ehrenberg's figure). 



Dimensions. — Length of the three joints, a 0-03, h 0-06, c O'l ; breadth, a O'OS, I 0-09, c 015. 



Habitat. — Fossil in Barbados. 



5. Dictyopodium thyrsolophus, n. sp. (PI. 73, fig. 7). 



Shell subeonical, rough, with two slight strictures. Length of the three joints = 1 : 2 : 4, 

 breadth = 1:3:6. Cephalis hemispherical, with an elegant horn, which is half as long as the shell, 

 spindle-shaped and scaly on the distal third. Thorax hemispherical, with small, regular, 

 circular pores. Abdomen inflated, papillate, with regular, circular pores, three times as large as 

 the thoracic pores (five to six in the course of its length). Feet slightly divergent, cylindrical, about 

 as long as the shell, shovel-shaped and fenestrated (with a prominent middle rib) at the distal end. 



Dimensions. — Length of the three joints, a 0"03, h 0-06, c 0'12 ; breadth, a 0'04, I 01, c 018. 



Hahitat. — Central Pacific, Station 268, depth 2900 fathoms. 



Subfamily 2. Theoperida, Haeckel, 1881, Prodromus, p. 436. 



Definition. — P odocyrtida with the basal mouth of the shell fenestrated (vel 

 Tricyrtida triradiata clausa). 



Genus 595. Lithornithium,^ Ehrenberg, 1847, Monatsber. d. k. preuss. Akad. d. 



Wiss. Berlin, p. 54. 



Definition. — T li e o p e r i d a (vel Tricyrtida triradiata clausa) with three solid lateral 

 wings on the thorax. 



The genus Lithornithium has an ovate or spindle-shaped shell, with two distinct 

 strictures, and tapering towards both poles. The abdomen is simple, whilst the 

 cephalis bears an apical horn, and the thorax three free, lateral, solid, divergent wings. 

 It may be derived from Pterocorys by development of a terminal lattice-plate closing 

 the mouth. 



1. Lithornithium ciconia, n. sp. (PI. 67, fig. 3). 



Shell nearly spindle-shaped, with two indistinct strictures. Length of the three joints = 

 1:2:4, breadth =1:3:3. Cephalis ovate, with a large pyramidal spine of twice the length. 

 Thorax three-sided pyramidal with three pyramidal wings of the same length, the broad triangular 

 bases of which occupy the whole length of the thoracic edges. Abdomen inversely ovate (in the 



1 Lithor7tithium = Si\iceo\xs bird ; T^lSos, o^'/iHiov. 



