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



family Ammoconidae (PL VIII.). They correspond to the Homocoela or Asconidse 

 among the Calcarea, and are, like these, thin-walled porous tubules, " without separate 

 flagellated chambers, the whole of the inner surface being covered with flagellated 

 cells." 1 The different forms of these Cannocoela, which I could distinguish, may 

 be disposed into three different genera (Ammolynthus, Ammosolenia, and Ammoconia), 

 and these correspond to the three genera which I have described in my Monograph 

 of the Calcisponges as Olynihus, Leucosolenia (or Soleniscus), and Auloplegma. 



All the other Keratosa of the deep sea are of larger size, and belong to the second 

 order, Domatoccela. They correspond to the calcareous Heteroccela of Polejaeff, and 

 possess, like these, " separate flagellated chambers lined with flagellated cells, the 

 remaining parts of the inner surface being covered with pavement-epithelium." The 

 Domatoccela of the deep sea may be disposed into three different families : Psam- 

 minidse, Spongelidae, and Stannomidse. The Psamminidse (Psammina, Holopsamma, 

 Psammopemma) produce no spongin-fibres ; their pseudo-skeleton is composed of 

 xenophya or of foreign bodies, which are crowded in the ground-mass of the mesoderm. 

 The Spongelidae (Cerelasma, Psamrnophyllum) possess a network of spongin-fibres 

 which enclose foreign bodies. The Stannomidse, finally, are distinguished by fine 

 bundles of fibrillar, between which the xenophya are crowded in the maltha (Stanno- 

 phyllum, Stannarium, Stannoma). 



Synopsis on the Four Families of Deep-Sea Keratosa. 



I. CANNOCCELA. 



Tubular canal-system, on the 

 Asconal-type (similar to the 

 AscouicUe). 



II. DOMATOCCELA. 



Vesicular canal-system, on the 

 Leueonal-type, with large fla- 

 gello chambers (similar to the 

 Spongelidre). 



f 



f 



No spongin- 

 skeleton. 



Pseudo-skeleton composed of xeno- 

 phya, which are crowded in the 

 maltha, .... 



, T . ( Pseudo-skeleton composed of xeno- 



No spongin- 1 , , . , * , , . ,, 



, f . ° J phya, which are crowded in the 

 skeleton. I x \.! 



( maltha, .... 



Spongin- 

 skeleton com- 

 posed of horny 

 fibres, fibrillce 

 or lamellae. 



Spongin-skeleton reticular, composed 

 of anastomosing fibres, including 

 xenophya, 



Spongin-skeleton fibrillar, composed 

 of fibrillin, not anastomosing, and 

 never including xenophya, 



1. Ammoconidj;. 



2. PSAMMINIDiE. 



3. Spongelidje. 



4. Stannojiid.e. 



1 hoc. tit., p. 35. 



