1512 THE VOYAGE OF H.M.S. CHALLENGER. 



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Genus 653. Cyrtocapsa, 1 Haeckel, 1881, Prodromus, p. 439. 



Definition. Stichocap sida (vel Stichocyrtida eradiata * clausa) with an apical 

 horn on the cephalis, without basal terminal spine. 



The genus Cyrtocapsa and the two following genera represent together the small sub- 

 family of Stichocapsida, or of those Cyrtoidea in which the many-jointed shell bears 

 no radial appendages, and the terminal mouth is closed by a lattice-plate. They have been 

 derived from the Stichocorida by development of such a closing plate. Cyrtocapsa bears 

 an apical horn on the cephalis, and may be derived therefore directly from Eucyrtidium. 



Subgenus 1. Cyrtocapsella, Haeckel. 



Definition. Shell with three annular strictures (or internal septa) and four distinct 

 joints. 



1. Cyrtocapsa tetrapera, n. sp. (PI. 78, fig. 5). 



Shell rough, pear-shaped, with three deep strictures. The three first joints are of equal lengths, 

 and each half as long as the hemispherical fourth joint. Cephalis subspherical, with an oblique 

 conical horn of the same length. The third joint is the broadest, three times as broad as long. 

 Pores regular, circular. 



Dimensions. Length of the shell (with four joints) 015, breadth 0'09 ; length of each of the 

 three first joints 0'03, of the last 0'06. 



Habitat. Western Tropical Pacific, Station 225, depth 4475 fathoms. 



2. Cyrtocapsa compacta, n. sp. (PI. 77, fig. 8). 



Eucyrtidium compadum, Haeckel, 1878, Atlas, loc. cit. 



Shell rough, pear-shaped, with three slight strictures. The hemispherical cephalis bears a thick 

 pyramidal spine of the same length, and is half as long as the second and the third joints, one- 

 third as long as the hemispherical fourth joint. The third joint is the broadest, three times as 

 broad as- long. Pores subregular, circular. In the centre of the basal pole is one larger pore, the 

 remnant of the constricted mouth of Ewyrtidium. 



Dimensions. Length of the shell (with four joints) 016, breadth 012. Length of the single 

 joints, a 0'02, b 0"04, c 0'04, d 0'06. 



Habitat. Western Tropical Pacific, Station 206, depth 2100 fathoms. 



1 Oyrtocapsa= Basket-capsule ; xvfrc;, x*^*. 



