206 



GEODINELLA ROBUSTA. 



The specimens of var. carolae (Plate 1, figs. 12, 17) are both incrusting 

 cushion shaped and nearly of the same size, about 45 mm. long, 30 mm. broad, 

 and 15 mm. high. From the margin of the base of the specimen from Naha 

 Bay (Plate l, fig. 12) several processes arise. One is large and digitate, 23 mm. 

 long and 7 mm. thick at the base; the others are small. The surface is slightly 

 uneven, covered with low rounded elevations. On the summit of some of the 

 more pronounced elevations a circular aperture, up to 700 /x in diameter, is ob- 

 served. This leads into a rather wide cavity, constricted below by a chonal 

 sphincter. The appearance of some of the elevations, not thus provided with an 

 apical vent indicates that these also possessed such an aperture which has, 

 however, been quite closed by contraction. The specimen of var. megasterra 

 (Plate 1, fig. 16) is somewhat irregularly finger shaped, slightly bent, and 43 

 mm. long. It is at the base 16 mm. thick; towards its upper end it tapers to a 

 diameter of 10 mm. The surface has the same character as that of the specimens 

 of var. carolae, the only difference being that the apertures on the elevations at- 

 tain a larger size, the widest measuring as much as 1.5 mm. in diameter. The 

 specimen of var. ynegadada is 13 mm. in diameter and appears to be a fragment 

 (the tip) of a finger-shaped sponge like the specimen of var. megasterra. The 

 largest apertures on its surface are 300 /( wide. The specimens of var. mega- 

 sterra and of var. carolae from Naha Bay are partly covered by thin crusts of 

 a monaxonid sponge. In both these varieties examination of the surface with a 

 lens shows here and there indications of hirsute spicules, broken off short; 

 since, however, I have been unable to find in the sections any spicules penetrating 

 the cortex, it is doubtful whether these broken, apparently hirsute, spicules 

 are proper to the sponge. 



The colour is white or white with a brownish tinge on the surface and dirty 

 white or brownish in the interior. The surface of the two specimens from Naha 

 Bay is partially covered with a darker brown coating which may be foreign to 

 the sponge. 



A hard cortical layer, composed of dense masses of sterrasters, a sterraster- 

 armour (Plate 1, figs. 21a, 24a; Plate 2, fig. 6a), surrounds the choanosome. 

 This cortex is 1-2 mm. thick in var. megaclada on the whole somewhat thicker 

 than in the other two varieties. 



Canal-system. The sterraster-armour (cortex) is perforated by round or 

 oval holes 300 /(-1. 5 mm. wide. Each perforation is traversed by a radial canal 

 situated centrally. This canal may be wide and extend nearly to the sterrasters 

 surrounding the perforation through which it passes, or it may be contracted, 



