250 MYRIOZOID^. 



The direction in vvliich the mandible of the avicularium 

 points is also very variable in this species : most commonly 

 it is placed transversely; but very often it is turned straight 

 upwards^ or obliquely downwards or outwards. 



The mucronate process_, which is often present below 

 the mouth, is likewise subject to many diversities in the 

 degree of its development. In some cases it is absent 

 altogether ; in others it is small and inconspicuous ; in 

 others again (as in the var. crucifera) it rises into a tall 

 and slender spine, which gives off one or more branches. 

 In this form it is occasionally double ; the ovicell is 

 sometimes developed round one of the two spines, the 

 extremity of which appears as a spike-like process on the 

 front of it. In the Mediterranean variety {nitida) the 

 mucro is large and massive, and traversed by radiating 

 ridges. 



The variety hastata presents some very striking features ; 

 and I at one time regarded it as a distinct species. The 

 tall mucronate processes, each with a rather large lateral 

 avicularium at the base, are profusely developed; the 

 orifice has a broad sinus on its inferior margin; the 

 zoarium is usually white and silvery ; and the surface is 

 covered with large punctures, which often assume a 

 radiated arrangement. The ooecium has not unfrequeutly 

 a mucro at the top. 



Habitat. Under stones, near low-water mark, and on 

 shells, stones, &c., and more rarely on Algse, from shallow 

 to very deep water. 



Localities. Very abundant and generally distributed. 

 Shetland, common down to 170 fathoms. Var. crucifera: — 

 On a shell dredged in 40-50 fathoms off Unst (A. M. N.) : 

 Orkney (Barlee) : Ireland, north and west (W. T.) : Bir- 

 terbuy Bay (G. S. Brady) : Beaufort Dyke, 110-147 

 fathoms (Capt. Beechey) : Filey, Yorkshire, between tide- 



