SPONGES. 69 



choanosome contain numerous pigment cells full of brown granules, especially in the 

 walls of the canals. The material is not sufficiently well preserved to show the 

 characters of the flagellate chambers. The inhalant pores, about 0'13 millim. in 

 diameter, are the single openings of short cylindrical chones which penetrate the 

 spicular dermal crust and are provided with well -developed sphincters near its inner 

 limit ; but there are no extensive subcortical crypts. 



(A fragment of a large, massive anatrisene was found in a boiled-out preparation of 

 the spicules of this sponge, but I could find no others, either in boiled-out preparations 

 or in sections. Should this form of spicule prove to be proper to the species, it would 

 necessitate its removal from the genus Plakinastrelld). 



R.N. 224 (from Station XLL, 12 miles off Galle, 100 fathoms). 



Plakinastrella schulzei,* n. sp. Plate II., fig. 3. 



This well-characterised species is represented in the collection by an irregular 

 massive specimen (or fragment) which has been cut off at the base from its attachment. 

 The upper surface is strongly convex and is produced into irregular elevations. The 

 specimen contains many foreign organisms, both internally and encrusting the surface 

 (it is penetrated by the spiral shells of a species of Tenagodes (Siliquaria), a gastropod 

 which habitually lives in sponges). The colour is purplish grey externally (owing to 

 the presence of numerous granular pigment cells), yellowish within. The vents are 

 irregularly scattered, well-defined circular openings, which may be crateriform ; up to 

 about 3 millims. in diameter, but usually a good deal smaller. Inhalant pores (?) are 

 rather conspicuous on some parts of the surface, but irregularly scattered and varying 

 much in size. The specimen measures about 50 millims. in length, 30 millims. in 

 breadth, and 18 millims. in thickness. 



The main skeleton is a very irregular interlacement of numerous large oxea and a 

 few short-shafted trisenes ; the spicules occasionally forming loose wisps. The 

 dermal skeleton is a dense feltwork of small oxea. 



Spicules. (1.) Short-shafted trisenes (Plate II., fig. 3, a-d), resembling calthrops 

 and subject to much variation in form ; commonly with three rays long and bifid and 

 the fourth short and simple, all fairly sharp-pointed ; or all the rays may be simple ; 

 or one only may be bifid ; or one may be trifid, and doubtless other variations could 

 be found. Total diameter measured up to about 0'68 millim. from apex to apex of 

 rays, with primary rays about 0'046 millim. thick. 



(2.) Oxea (Plate II., fig. 3, e-t). The large oxea of the main skeleton (e) are stout, 

 fusiform and gradually sharp-pointed at each end ; more or less curved and occasionally 

 slightly angulated at two points, but not centrotylote. They measure, when fully 

 developed, about 1'3 millims. by 0'055 millim. The small dermal oxea (r, s, t) are 

 commonly centrotylote, more or less sharply pointed at each end, and with the two 

 terminal thirds bent upon the middle third at slight angles in the same direction ; 



* Named in honour of the most eminent of Spongologists, Professor F. E. SCHULZE. 



