1450 THE VOYAGE OF H.M.S. CHALLENGER. 



Dimensions. — Length of the shell (with eleven joints) 0-28, breadth 0-09 ; length of the tenth 

 joint 0'02, of the last joint 0"1. 



Hahitat. — Central Pacific, Station 271, depth 2425 fathoms. 



Genus 634. Cyrtopera} Haeckel, 1881, Prodromus, p. 439. 



Definition. — S tichoperida (vel Stichocyrtida triradiata clausa) with three 

 latticed lateral wings, or three longitudinal rows of lattice-wings. Cephalis with 

 a horn. 



The genus Cyrtopera differs from tlie preceding Stichopera in the fenestration of 

 the three lateral wings, and bears therefore to it the same relation that Sethornithium 

 exhibits to Lithornithium among the Tricyrtida. 



Subgenus 1. Artopera, Haeckel, 1881, Prodi-omus, p. 438. 

 Definition. — Shell with three annular strictures and four joints. 



1. Cyrtopera thoracoptera, n. sp. (PI. 75, fig. 3). 



Artopera tlwracoptei-a, Haeckel, 1881, Prodromus et Atlas {loc eit.). 



Shell inflated, with three very deep strictures. Length of the four joints = 2:7:8:6. Cephalis 

 hemispherical, with a slender, prismatic horn, half as long as the shell. Thorax subspherical, in 

 its middle third with three latticed, triangular wings of half the length. Abdomen with inflated 

 third, and inversely hemispherical fourth joint ; the third is the broadest. Pores subregular, 

 hexagonal, with thin bars. 



Dimensions. — Length of the shell (with four joints) 0'23. Breadth of the third (broadest) joint 

 013. Length of the single joints, a 0'02, h 0-07, c 0-08, d 0-06. 



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



2. Cyrtopera ornithoptera, n. sp. 



Shell broadly ovate, with three slight strictures. Length of the four joints = 1:2:3:4. 

 Cephalis hemispherical, with a slender, pyramidal horn of three times the length. Along the 

 second and third joints arise with broad base three latticed, triangiJar wings, nearly as long as the 

 whole shell. Abdomen inflated. The fourth joint is the broadest and longest, with hemispherical 

 basal pole. Pores subregular, hexagonal. (Similar to Artopilium longicornc, PI. 77, fig. 10, but 

 with more closely reticulated network, and perfectly closed mouth.) 



Dimensions. — Length of the shell (with four joints) 0'2. Breadth of the fourth (broadest) joint 

 014. Length of the single joints, a 0-02, b 0-04, c 0-06, d 0-08. 



Habitat. — Central Pacific, Station 274, depth 2750 fathoms. 



' Cyrtopera = Basket-poucli ; xi/^ro;, 9r^j«. 



