HICKSON— POLYTREMA 455 



S. cylindricurn, facies Providentise. 



Providence (D. 7) 70 fathoms. Several large specimens (Plate 30, tig. 3). 

 S. cylindricurn, facies Amirantise. 



Amirante (E 1) 29 fathoms, 2 specimens. 



Amirante (E 2) 29 fathoms. 



Amirante (E 9) 34 fathoms (Plate 30, fig. 6). 



Amirante (E 12) 32 fathoms. 



Amirante (E 13) 20—22 fathoms." 

 All the above are salmon colour. 



Saya de Malha (C 1) 150 fathoms. 



Saya de Malha (C 16) 26 fathoms, 2 small specimens (Plate 30, fig. 7). 

 Providence (D. 4. 10. 05) 50—78 fathoms. 

 Cargados Carajos (B 9) 30 fathoms. 

 The above are orange coloured. 



The type of the species is red in colour and belongs to the "Amirante" facies. It 

 came from the Gulf of Manaar. In the British Museum there is an orange coloured specimen 

 of the Amirante facies from the Macclesfield bank. 

 S. cylindricurn, facies Saya de Malhensis. 

 Saya de Malha (C 16) 26 fathoms. 

 Saya de Malha (C 19) 29 fathoms (Plate 30, fig. 4). 

 Providence (D. 4) 78 fathoms. 



In the British Museum there is a specimen of this facies, locality unknown. 



Sporadotrema rnesentericum (Carter). 



This species is found in Torres Straits (Plate 30, fig. 5). 



V. SOME NOTES ON STRUCTURE. 



The siliceous spicides. All the specimens of the three genera I have examined have 

 the habit of picking up and incorporating the siliceous spicules of sponges. This habit is 

 not peculiar to these genera but occurs in other genera, such as Carpenteria ; and it is 

 probably comparable with the habit of picking up sand grains and other foreign bodies by 

 the arenaceous Foraminifera, as in some cases I have found grains of sand and the frustules 

 of Diatoms (Coscinodiscus, etc.) enclosed in the chambers. Lister (11) speaks of the sponge 

 spicules taken up by Pol ytrema as " a temporary scaffolding for the support of the extended 

 pseudopodia, in advance of the proper wall." The number of sponge spicules seen in different 

 specimens varies very considerably. In many specimens of Sporddotrema the spicules are 

 so numerous that the free edges may be said to bristle with them, in others only a few 

 scattered spicules may be observed. (Some of the spicules may be faintly seen in Plate 31, 

 fig. 16.) In the chambers broken fragments of siliceous spicules are invariably found but 

 in the solid calcareous walls of the chambers and particularly in the central hard core of 

 the larger specimens of Sporadotrema very few spicules can be found. It is difficult to 



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