644 REVISION OF THE AXINELLID^, iii., 



External characters. — The single specimen (PI. xxix., fig. 3) is 

 irregularly cake-shaped, with the upper surface deeply incised by 

 several narrow, valley-like or sulciform grooves, and measures 

 65 mm. in length, 45 mm. in breadth, and 35 mm. in height in 

 its most elevated, central portion; the grooves appear to be due 

 merely to the more rapid upgrowth of the intervening portions 

 of the sponge, and thus to be of accidental origin. The surface 

 is further rendered uneven by many irregular shallow furrows 

 and slight undulations, and by moderately numerous, ii'regularly 

 scattered, small papilliform conuli; the latter are usually more or 

 less appi'essed to the surface, and seldom exceed 1 mm. or so in 

 height. The dermal membrane is distinct and easily separable 

 (owing to the presence of subdermal spaces), and over most por- 

 tions of the surface presents, to the naked eye, a minutely reticu- 

 late pattern (PI. xxxviii., fig. 8), due to the mode of arrangement of 

 the dermal pores. Interiorly, the sponge is travei'sed more or less 

 vertically by numerous, fairly wide, main efferent canals (up to 

 4 mm. in diameter), which terminate in relatively rather small 

 oscula situated, for the most part, on the more elevated portions 

 of the surface. For some distance before arriving at the oscula, 

 many of the canals run close beneath the surface, separated from 

 the exterior by scarcely more than the dermal membrane. 



The consistency in alcohol is rather soft and compressible, 

 imperfectly resilient, somewhat lacking in toughness, but not 

 brittle; and the colour is Ijrownish-grey on the surface, slightly 

 paler in the interior. 



The dermal reticulation (PI. xliv., figs. 1, 2) is made up of more 

 or less polygonal meshes, varying in actual shape, in different 

 portions of the surface, fi'om nearly circular (with a diameter of 

 from rarely less than 120 to occasionally 250/;i) to almost oblong 

 (measuring up to 350/a in length and often less than half as broad 

 as long), and separated by usually relatively narrow boundaries 

 varying from 25 to rarely more than 90//. in width. The largest 

 meshes occur on those portions of the surface where the main 

 effei'ent canals run immediately below the surface. Within the 

 interstices of the meshes, the dermal mejiibrane is perforated by 



