34 BY THE DEEP SEA. 



figure of speech you will agree when I add that Dr. Bowerbank 

 published a work in three volumes dealing only with British 

 Sponges, and to these a supplementary posthumous volume, 

 edited by Dr. Norman, has since been added. 



Where the rocks rise high above the shore with their upper 

 portions tilted towards the cliffs, we shall find several species 

 incrusting the vertical or overhanging surfaces of these rocks, 

 such as Halichondria incrustans, whose buff-coloured bread-like 

 surface is diversified with slightly raised oscula. Its principal 

 spicules are knobbed at one end, in which respect it differs 

 from the similar Halichondria panicea which is peculiar in 

 having only one type of spicules a rounded rod, slightly 

 curved or quite straight, but pointed at each end. Ellis called 

 this species the Crumb-of-bread sponge, a name which is 

 reflected in the scientific cognomen panicea. It is one of the 

 most plentiful of the encrusting species, and may be readily 

 known by the greenish-yellow or distinctly green colour of its 

 extensive patches. 



Not far from the Crumb-of-bread will in all probability be 

 found the similar Sanguine sponge (Halichondria sanguinea), 

 of a bright red colour. The conical elevations of the oscula 

 in these species distinguish them readily from the plump, 

 though narrow bands of Microciona carnosa, a plentiful species 

 that creeps extensively between the other kinds, its pale red 

 branches being very unequal in width, and alternately con- 

 tracting and swelling out, joining and separating. This will be 

 found figured in the lower left-hand corner of our illustration 

 on page 29. 



A very noticeable species on account of its neat compact 

 shape will be found attached to various red seaweeds, with 

 which its whitish colour contrasts well. It is a small oval, 

 usually from a quarter to an inch in length, very flat, but yet 

 hollow, with a large vent at the free and larger end. This is 

 the Grantia compressa. Careful search among the indescri- 

 bable medley of " unconsidered trifles" that crust the rocks 



