132 Proceedings of the Royal Trish Academy. 



dirt and mucus, and is sometimes radially striate. In the case in which it is 

 best developed, its diameter and depth amount only to about 17 cm. It is 

 quite thin-walled, thus differing completely from the body-wall. The body is 

 practically shapeless, its form when best preserved being that of a wide dish 

 with a short thick stem. In all cases the dish-like part is bi-lobed, the two 

 halves folding up against one another rather like the two valves of a lamelli- 

 branch. Reference to the half of an animal which is represented in PL XY, 

 figs. 1 and 2, will make ii clear that the lwn halves of the animal are flat — ■ 

 fig. 1, as seen from the Bide (fig. 2), becomes much narrower. The thickness 

 of the body-wall is rather uneven, but in the most regular cases it increases 

 gradually from the edge of the pedal disc upwards, the maximum thickness 

 being reached about the margin; and this latter is so thick and unwieldy 

 that it rolls inwards over the tentacles and almost hides them. In one case 

 the mesogloea here was L*3cm. in thickness; it is Bofl and jelly-like and 

 whitish. M with tentacle bases. No verrucae, capitular 



Boi j surface more or less wrinkled, sometimes torn and 

 damaged. The flat oral disc is very wide, and since it is so large and the 

 tentacle- are reduced, the animal, when opened out, looks like the under-side 

 of a mushroom. D utacles, and actinopharynx are deep purplish-black. 



Disc thin-walled, mouth fairly large, not widely gaping ; lips prominent, 

 inopharynx ridged. Tentacles entirely marginal, very small for the size 

 of the animal— how they can he of any particular use to it. is difficult to 

 imagine. They are Bhort, slender, soft, tapering, acuminate. l£ach one is 

 connected with the margin of the body by a thick, white bridge or Lump of 

 mesogloea, which is developed on its aboral side at the base. The tentacles 

 are aria _ daily in ly, the bi the outer cycle being 



usually ped than those of the inner. Tlie size of the tentacles 



and the development of the bridges vary in some extent in different parts 

 <>f the rather uneven disc, and in most specimens sonic tentacles are missing— 

 perhaps torn off. But the inner tent submarginal, and seem to be 



on a level, so that one can trace no complicated arrangement such as is found 

 in Porponia, etc. Inline, qs whose 1 [ counted, the respective 



numbers were about 2 and 27E — that is, the total numbers. The disc 



is not many-lobed a.- in A. but its curious way of folding seems to be 



a permanent character in consequence of which it is bi-lobed. 



•. — ih .1/ These are in six cycle-, the sixth not 



fully formed; here and there "in- finds a pair even of a seventh cycle. Only 

 the first four cycles are at all large, and only the six primary pairs are perfect, 

 two of them being apparently directives. In consequence of the enlargement 

 of the oral, and reduction of the pedal disc, and the general flattening of the 



