SPONGES AVHITELEGGE. 47 I 



ESPERIOPSIS CANALIOULATA, sp. nov. 



(Plate xliii., fig. 7). 



Stations 41, 47, 48. 



Sponge stipitate, much branched, and here and there coalescent. 

 The branches are subcylindric or slightly compressed proximally in 

 the plane of branching, and the distal two-thirds of each exhibits 

 a very distinct longitudinal groove which tei'rainates at the 

 summit. 



The surface generally is covered with a tough leathery-looking 

 epidermis without any visible pores. The oscula, if present, are 

 closable and situated at the apices of the grooves ; there are 

 several branches which exhibit a slightly puckered depression at 

 the summit, but no distinct opening that might be termed a vent. 

 In worn examples the channels in the branches exhibit a series 

 of subdermal pores about 1mm. or less in diameter. Texture 

 firm, somewhat resilient ; colour yellowish-grey. 



The skeleton when denuded presents a Raspailia-likQ surface, 

 but the network is reticulated. The mesh is generally oblong or 

 oval, and the axial region is occupied by several stout multi- 

 spicular fibres; the latter give off numerous secondaries which are 

 rather peculiar in shapeg they are broad at their origin, contracted 

 in the middle, and expanded at their extremities, forming a kind 

 of rosette-like structure, which supports the epidermis ; when the 

 latter is removed the projecting ends of the fibres give the surface 

 a peculiar bristly or villose aspect. The thickened epidermal 

 layer is furnished with numerous closely-arranged radiating 

 spicules ; when viewed from above many veiy small pores can be 

 seen between the tufts of surface spicules. 



The primary and secondary fibres consist of dense bundles of 

 spicules about 0-2 mm. thick; they are closely packed in a thin 

 layer of pale yellow spongin ; the connecting fibres are very 

 indefinite and consist of whispy masses of spicules, which extend 

 from the stouter fibres. The mesh measures from 5 to 1 mm. 

 in length, and is usually about 0-2 or 0-3 mm. in diameter. The 

 dense layer of epidermal spicules is 0-25 mm. in thickness. 



Megascleres : — straight smooth styli, variable in length and 

 diameter, the largest O'S by 0-001 mm., medium stouter kind 0-35 

 by 0-0018 mm.; styli of the epidermis 0-15 by 0-006 mm. Some 

 are subtylostyli with a very slight oval head. 



Microscleres : — minute isochelas 0-0014 mm. long, and toxa with 

 a well marked median bend about 0-02 mm. long. There are also 

 a number of straight toxodragmata present. 



