ME. A. DENDT ON WEST-INDIAN CHALININE SPONGES. 353 



II. Description of Genera and Species. 



Genus Pachtchalina, Schmidt. 

 18(j8. Pachychalina, Schmidt, Spongien der Kiiste von Algier, p. 8. 

 1886. DasycJialina, p. p., Ridley and Dendy, Ann. & Mag. Nat. Hist. ser. 5, vol. xviii. p. 3.29. 



Diagnosis. — Lobose or digitate, solid Chalininae ^. Fibres stout, with spicules 

 numerous and arranged polyserially. 



This diagnosis is not very satisfactory, but it is the best that I am able to give in 

 the present state of our knowledge ; for further information regarding the genus the 

 reader is referred to the Report on the Monaxonida of the 'Challenger' Expedition, 

 p. 19, where the question is fully discussed. 



Pachychalina variabilis, n. sp. (Plate LVIII. fig. 3 ; Plate LX. fig. 2.) 



This species is chiefly remarkable from its extreme variability in external form. It 

 is represented in the collection by five large specimens, each of which unites in itself 

 two distinct types of growth, lobose and digitate. The long, subcylindrical, digitate 

 processes may either be united at the base only with the compressed, lobose portions, 

 or they may arise from various parts of the surface of the same, or from the free 

 margin. One very remarkable example consists of a single, crescent-shaped, thick, 

 cushion-like lobe, 19 centim. high, 24 centim. broad, and 5 centim. thick in the 

 middle. The oscula occur thickly scattered over one surface only, and from near the 

 middle of the base, on the side opposite to that on which are the oscula, arises a single, 

 upright, thick, irregular, digitate process, constricted at intervals in a somewhat moniH- 

 form manner, with oscula irregularly scattered over the surface, but mostly on one side. 

 This process is a little taller than the lobose portion to which it is attached. 



The largest specimen in the collection consists of a great, irregular, broadly expanded 

 lobe, giving oflF from the base, from the free margin, and from various parts of both 

 surfaces a number of irregular, simple or branched, digitate processes. The oscula 

 occur for the most part scattered irregularly over one surface of the specimen. The 

 height of the entire specimen is about 38 centim., and the greatest breadth 37 centim. ; 

 while the average diameter of the digitate processes is about 2 centim. 



The colour (in the dry condition) of all the specimens is light yellowish grey, and 

 the texture hard, but fibrous and somewhat elastic. The oscula are large round 

 openings, with slightly raised margins, averaging about 5 millim. in diameter. In the 

 case of the lobose portions of the specimens they are almost entirely confined to one 

 surface, as is usually, if not always, the case in flabellate sponges. Sometimes also they 

 occur uniserially arranged along the margin of the sponge. 



The main skeleton (PI. LVIII. fig. 3) is a very irregular reticulation of strong spiculo- 

 fibre, containing both a large amount of spongin and a great number of spicules. 



' The term ChalininEe includes, according to my views, only sponges in which the megasclera, when 

 present, are diactinal, and there are no microsclera. 



