298 ESCHARID^J. 



outwards ; peristome elevated, thickened, unarmed, 

 forming a conspicuous border round the mouth, some- 

 times much raised, so as to be almost infundibulate, 

 and often rising on each side into a pointed process ; 

 commonly an umbo below the mouth. Frequently an 

 avicularium immediately under the inferior margin, with 

 semicircular mandible directed downwards. Ooecia 

 none (?) . 



Colonies forming large subcircular crusts. 



Primary cell small, the orifice occupying a large portion of 

 the front surface ; in other respects normal. 



Potypide with 16 slender tentacles, forming a rather deep 

 bell. 



RANGE OF VARIATION. The characters are on the whole 

 very constant. When old the crust is thickened and 

 coarsely reticulated ; occasionally the surface is traversed 

 longitudinally by raised anastomosing ridges. The umbo 

 below the mouth is often absent ; while at times it is 

 developed into a tall spike-like process. A variety occurs 

 in which the peristome is much produced; and in this 

 condition the species makes an approach to L. canthari- 

 formis, Busk (Plate XXIV. fig. 4) . The avicularia are 

 often wanting. 



HABITAT. On shells and stones (chiefly) between tide- 

 marks, and in very shallow water ; rarely in deeper water. 



LOCALITIES. Cornwall (C. W. P.) : South Devon, abun- 

 dant, the predominant littoral species on the south- 

 western coasts ; Guernsey ; Lul worth, under stones, on a 

 remarkably rough and barren shore ; Llandudno ; Isle of 

 Man, common (T. H.) : Jersey (Alder) : Tenby (Busk) : 

 Berwick Bay, very rare (Johnston) : Bamborough and 

 Cullercoats, Northumberland (Alder) : Thurso ; Wick 

 (C. W. P.) : Ayrshire (Landsborough) : Dublin Bay (Has- 

 Scill) : off the Copelands, Belfast Bay, deep water (W. 



