REPORT ON THE DEEP-SEA KERATOSA. 29 



end by an irregular broad basal plate. The mouth-opening — or the osculum (o) — on the 

 opposite distal end is circular, 2 mm. in diameter. The total length of the sponge is 

 15 to 20 mm. 



The opaque white body of this species is composed almost entirely of calcareous 

 shells of Foraminifera and their fragments. After being dissolved in dilute hydrochloric 

 acid, there remains a thin membranous wall, pierced by numerous small pores ( p). These 

 dermal pores are shown in fig. 2 in the complete body, although they are not distinct 

 until the removal of the calcareous matter. On the inside of the thin wall were visible 

 fragments of delicate epithelium, composed of small granular cells ; these were, however, 

 not so distinct as in the closely-allied Ammoconia auloplegma (PI. VIII. fig. 4, n). 



Genus 2. Ammosolenia, 1 n. gen. 



Definition. — Ammoconidas with arborescent body, forming tubular branches, which 

 are not connected by anastomoses. Each branch with a terminal opening (osculum). 



The genus Ammosolenia is derived from the preceding Ammolynthus by branching, 

 and therefore bears the same relation to it as among the Calcarea Leucosolenia (or, more 

 strictly speaking, Soleniscus) does to Calcolynthus. The branched or arborescent body 

 of the tubular sponge bears a number of thin-walled porous branches, and each of these 

 has on the distal end a wide simple mouth-opening. Branched tubes like these are not 

 rare in many deep-sea soundings of the Challenger collection, and are described by Brady 

 in his .Report on the Foraminifera (p. 274, pi. xxviii.) under the name of Rhizam- 

 mina algseformis. Their arenaceous pseudo-skeleton is usually composed of Globigerina 

 ooze, as also in our Ammosolenia rhizammina. But two important differences separate 

 the latter from the former. The thin wall of the arenaceous sponge (Ammosolenia) is 

 pierced by numerous small pores or inhalent openings (fig. 4, p), whilst the solid wall 

 of the similar arenaceous Rhizopod (Rhizammina) is not perforate. The cavity of the 

 branched tubes is lined in the former by a flagellated epithelium, filled up in the latter 

 by simple sarcode or protoplasm. It must be recorded, however, that this sarcode, as 

 the most important part, in Rhizammina as well as in many other large arenaceous 

 Foraminifera, has not been demonstrated by observation, but only assumed theoretically. 

 It may be, therefore, that many of these latter belong to our Ammoconia or similar 

 Ammoconidas. 



Ammosolenia rhizammina, n. sp. (PL VIII. fig. 3). 



Habitat— Tropical Pacific, Station 216a; February 16, 1875; lat. 2° 56' N., long. 

 134° 11' E.; depth, 2000 fathoms; bottom, Globigerina ooze. 



1 Ammosolenia = Arenaceous tubes, «,«,««, ou^tjuioi/. 



