OF THE KERGUELEN REGION OF THE GREAT SOUTHERN OCEAN. 379 



MONAXONIDA : 



* Axoniderma mirabile, Ridley and Dendy. 

 # Cladorhiza inversa, 1 Ridley and Dendy. 

 Esperella biserialis, 2 Ridley and Dendy. 



Phakellia 3 ventildbrum 4 (Johnston), var. connexiva, Ridley and Dendy. 

 * Tedania 5 actiniiformis? Ridley and Dendy. 

 '* Trichostemma 1 irregularis, Ridley and Dendy. 



Tetractinellida : 



*Thenea ivrightii, Sollas. 

 „ sp- (?)■ 



Hexactinellida : 



*Bathydorus baculifer, Schulze. 

 *Caidocalyx tener, Schulze. 

 *Holascus stellatus, Schulze. 



1 The most remarkable feature about Cladorhiza inversa concerns its external form ; compared with other 

 " Crinorhiza" forms it appears to be upside down; nor can we be certain that the surface which we have called 

 " lower " in the description is not really the upper, and vice versa. — (Ridley and Dendy, Zool. Chall. Exp,, part 59, 

 p. 94.) 



2 Esperella biserialis forms a most interesting and important link between the two genera Esperella and Cladorhiza, 

 especially as regards external form. It is also particularly interesting in that it exhibits a distinctly bilateral 

 symmetry. — (Ridley and Dendy, Zool. Chall. Exp., part 59, p. 76.) 



3 We have thought it desirable in the case of the genus Phakellia to make use of external form as a generic 

 character, otherwise we know of no character which would serve to separate the genus Phakellia from the genus 

 Axinella. — (Ridley and Dendy, Zool. Chall. Exp., part 59, p. 170.) 



4 Phakellia ventildbrum is typically an inhabitant of deep water, being common in depths over 100 fathoms, 

 seldom occurring in shallower water, and going down to 1035 fathoms, as shown by the Challenger dredgings. — 

 (Ridley and Dendy, Zool. Chall. Exp., part 59, p. 171.) 



5 The range of external form exhibited by the genus Tedania is shown by the Challenger dredgings to be a very 

 remarkable one indeed ; hitherto known only by more or less massive or digitate specimens, we have had to add to 

 the genus two new species, T. infundibuli/ormis and T. adiniiformis, characterised by very specialised, though quite 

 different, external forms ; the former being funnel-shaped, and the latter " actiniiform " (like an Actinia) with oscular 

 projections on the top and a definite zone of pores. The species of this genus are very difficult to separate satisfactorily 

 from one another ; future researches may, very probably, by the discovery of intermediate forms, render possible the 

 union of some which are at present described as distinct. — (Ridley and Dendy, Zool. Chall. Exp., part 59, pp. 50-51.) 



6 Tedania adiniiformis is a very important and well-characterised species ; it is distinguished from all previously 

 known by its external form and the arrangement of the pores in a definite zone. Its stylote spicule is the largest in 

 the genus. It affords a really splendid instance of the manner in which sponges, which are shapeless masses when 

 occurring in shallow water, assume in abyssal depths (in this case 2160 fathoms) a definite, symmetrical external form ; 

 this is its chief interest, for the species of the genus hitherto known, from comparatively shallow water, are, par 

 excellence, amorphous sponges. — (Ridley and Dendy, Zool. Chall. Exp., part 59, p. 56.) 



7 The. original type of the genus Trichostemma is Trichostemma hcmisphozricum, which occurs not rarely at Lofoten in 

 a depth of 120 to 300 fathoms on soft clay bottom. The Challenger adds two new species, both from a very great depth 

 and a bottom of ooze or mud. It is essentially a deep-sea genus, and affords another example of the manner in which 

 deep-sea sponges commonly assume a definite, symmetrical external form. In this case, however, the object of the 

 flattened form and the long radiating spicules is obvious, namely, as pointed out by Sars, to support the animal in the 

 soft mud on which it lies ; in our new species, Trichostemma sarsii, this arrangement is brought to a much greater 

 degree of perfection than in the original type of the genus. The genus has a very wide geographical range, being 

 found in deep water off the north of Scotland, coast of Norway, Arctic Sea, Gulf of St Lawrence, off the Azores, 

 N.E. coast of Australia, and W. coast of South America. — (Ridley and Dendy, Zool. Chall. Exp., part 59, p. 217.) 



