1646 THE VOYAGE OF H.M.S. CHALLENGER. 



The central capsule of the Challengerida is constantly placed in the aboral half of 

 the shell -cavity, whilst its oral half is occupied by the phseodium ; the intervals between 

 them and the inner surface of the shell are filled up by the calymma. Frequently 

 from the outer surface of the capsule arise numerous branched streams of sarcode, which 

 pierce the calymma and are directed towards the inside of the shell-wall, where they 

 are united by a thin continuous layer of protoplasm (PL 99, fig. 1). The phseodium is 

 usually more voluminous than the capsule and envelops the latter on its anterior or 

 oral face ; more rarely the entire capsule is hidden in the phseodium. The phasodella, 

 constituting the latter, are of very different sizes, of variable colour, olive and greenish - 

 brown, red-brown, black-brown or nearly black. In some preparations, stained with 

 carmine, numerous red coloured granula, similar to nuclei, were scattered in the 

 phseodium (compare Murray, loc. cit., PI. A, figs. 114). 



The diameter of the central capsule is usually about one-half or one-third as great as 

 that of the enclosing shell (PL 99, figs. 120). Its form is either spherical or slightly 

 compressed, spheroidal, or sometimes lenticular. The large nucleus has the same form, 

 is about half as broad as the capsule and contains numerous nucleoli. Sometimes the 

 capsule contained two nuclei of equal size, and in a few specimens the shell contained 

 two central capsules, each with a nucleus, so that the Challengerida seem to propagate 

 also by self-division (PI. 99, fig. 6). 



The astropyle, or the large opening of the central capsule, exhibits the usual radiate 

 operculum of the PHJSODARIA, and the tubular proboscis arising from it. This is 

 constantly placed on the oral or anterior pole of the capsule and directed towards the 

 mouth of the shell. I was never able to discover any parapyle or secondary opening 

 in the central capsule, though numerous and well-preserved specimens of the Challenger 

 collection were accurately examined. It seems therefore that the Challengerida are not 

 TRIPYLEA (as the majority of PH^EODARIA), but MONOPYLEA with a single opening (like 

 the closely allied Medusettida and Castanellida). 



Synopsis of the Genera of Challengerida. 



I. Subfamily f Shell smooth, without adoral teeth and marginal spines, . 693. Lithogromia. 



Lithogromida. 



Shell without pharynx or \ Shell with adoral teeth, but without marginal spines, . 694. Challengeria. 



inner prominent tube of | 

 the mouth. [ Shell with adoral teeth and with marginal spines, . . 695. Challengeron. 



II. Subfamily 



Pharyngellida. 

 Shell with a pharynx, or 

 an inner cylindrical tube, 



Shell smooth, without adoral teeth and marginal spines, . 696. Entocannula. 

 Shell with adoral teeth, but without marginal spines, . 697. Pharynyella. 



ind 3*r ; t ' 'd Shell with adoral teeth and with marginal spines, . . 698. Porcupinia. 



