REPORT ON THE DEEP-SEA KERATOSA. 7 



historical introduction given by Vosmaer. 1 Lendenfeld 2 divides the order Keratosa 

 (Bowerbank) into two suborders (called by him tribus 3 ), and these into six families, 

 viz.: — 



I. Microcamerse, with small spherical ciliated chambers and opaque ground-mass 

 (1. Family Spongidse ( = Euspongidse), 2. Family Aplysinidse, 3. Family Hircinidse). 



II. Macrocamerse, with large sac-shaped ciliated chambers and soft transparent 

 ground-mass (4. Family Spongelidse, 5. Family Aplysinidse, 6. Family Halisarciclse). 



Vosmaer adopts only four families among his Ceratina, viz.: — -1. Spongelidse, 

 2. Spongidse ( = Euspongidse), 3. Aplysinidse, 4. Darwin ellidse ( = Aplysillidse, Lenden- 

 feld). These latter are distinguished by dendritic spongin-fibres not anastomosing, 

 while the branched spongin-fibres in the three former families anastomose and form a 

 reticular skeleton. Among these the Spongelidse possess a soft transparent ground- 

 mass (or maltha), not granular, whilst it is granular and opaque in the Euspongidse 

 and Aplysinidse. These two families differ again in the structure of the anastomosing 

 spongin-fibres, which are homogeneous, with a thin axial thread in the Euspongidse, 

 whereas they are heterogeneous, tubular, with an axial pith-substance in the Aplysinidse. 



A single family only of those enumerated is represented among the Deep-sea 

 Keratosa collected by the Challenger. This is the family Spongelidse (with two new 

 genera, Cerelasma and Psammophyllum). The sandy Keratosa, Psammopemma and 

 Holopsamma, hitherto united with the Spongelidse, must be separated from them, 

 since they produce no spongin at all ; they compose (together with the new genus 

 Psammina) our family Psamminidse. A new family is formed by the remarkable 

 Stannomidse, the largest and most striking among the Deep-sea Keratosa ; their 

 spongin-skeleton is never reticular, but formed by bundles of delicate fibrillse, which 

 never anastomose ; the sandy xenophya are not enclosed by the fibres, but lie between 

 them in the maltha. Not less interesting is a fourth new family, that of the Ammo- 

 conidse, distinguished from all the others by the simple structure of their canal-system, 

 formed on the Ascon-type. 



Respecting this latter most important difference, all the Deep-sea Keratosa collected 

 by the Challenger belong to two main groups of very unequal range, and these corre- 

 spond perfectly to the two orders or main groups of calcareous sponges which Dr. 

 Polejaeff, in his Report on the Calcarea 4 dredged by H.M.S. Challenger, has 

 distinguished as Homocoela and Heterocoela. The first order (Cannoccela) is repre- 

 sented by only a few, and small, but most interesting Keratosa, constituting our 



1 Vosmaer, Bronn's Klassen und Ordnungen des Thier-Reichs, ed. 2, Bd. ii. (Porifera), pp. 17-109, 1887. 



2 Lendenfeld, On the Systematic Position and Classification of Sponges, Proc. Zool. Soc. Lond., December 21, 1886; 

 Der gegenwartige Zustand unserer Kenntniss der Spongien, Zool. Jahrb., 1887, p. 511. 



3 The term tribus is generally employed for smaller sections of a family, therefore subordinate to the latter term. 

 Compare my Generelle Morphologie, Bd. ii. p. 400, Berlin, 1866. 



4 Zool. Chall. Exp., pt. xxiv. p. 35. 



