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



Genus 383. NasseUa,'^ nov. gen. 



Definition. — Nassellida with foamy calymma, containing numerous large 

 extracapsular alveoles. 



The genus Nassella differs from the preceding Cystidium, its probable ancestral 

 form, in the development of numerous large alveoles in the extracapsular calymma, and 

 therefore exhibits the same relation to it that Thalassicolla bears to Actissa among the 

 Spumellakia. The foamy calymma is very voluminous, and includes numerous 

 symbiotic xanthellse. 



1. Nassella thalassicolla, n. sj). 



Central capsule spherical. Podoconus with simple circular porochora, half as long as the 

 capsule. Nucleus spherical. Numerous oil-globules in the endoplasm. Calymma spherical, 

 without pigment, with numerous xantheUte and large alveoles. 



Dimensions. — Diameter of the central capsule 012, nucleus 004, calymma 0-6. 



Habitat. — South Pacific, Station 300 (off Juan Fernandez), surface. 



2. Nassella nassiterna, n. sp. 



Central capsule ovate. Podoconus two-thirds as long as the capsule, trifid, with three equal 

 circular lobes (as in Cystidimn inerme). Nucleus ovate. Three equal large oil-globules in the 

 endoplasm, corresponding to the three lobes of the porochora. Calymma ovate, in the upper half 

 much more voluminous than in the lower, including nimierous large alveoli and xanthellse, and 

 around the mouth masses of black pigment. 



Dimensions. — Diameter of the central capsule O'l, nucleus O'Oo, calymma 0'8. 



Habitat. — Indian Ocean, Madagascar (Eabbe), surface. 



Suborder II. PLECTOIDEA, Haeckel. 



Plectoidea vel Plectida, Haeckel, 1881, Prodromus, p. 423. 



Plagiacanthida {sensu ampliori), R. Hertwig, 1879, Organismus d. Radiol., p. 72. 



Definition. — Nassellaria with a rudimentary, originally tripodal skeleton, composed 

 of radial spines, arising from one common central point or central rod ; the spines are 

 simple or branched, and the branches may form by concrescence of their meeting ends a 

 loose wickerwork, but never a complete lattice-shell. Never a ring in the skeleton. 



' i\'cMS(!Zto — Small wicker cage for flsbinc. 



