1 44: Proceedings of the Roi/al Irish Academy. 



slightly marker! off from the lower part, as a "capitulum," by the cessation of 

 the seapal tubercles : the line of demarcation is more or less distinct in 

 different specimens. This zone is provided with longitudinal ridges, which 

 may be distinct and crest-like, and may be continuous or broken up by 

 transverse interruptions into tubercles, or may lie nearly obsolete; some are 

 large, some divided, some almosf invisible, even in different parts of one 

 animal. Although their number is to some extent related to that of ihe 

 tentacles, there is as a rule no regularity or plan of development at all. All 

 the thickened white aboral swellings of mesogloea, and these 



of the ■ re continuous with the margin. The oral disc is 



peculiar; in all cases it is bi-lobed i PI. XIV, fig. 6, show- one hill' or lobe of 

 a specimen), rathei wavy in outline. and the two lobes, which have theiredges 

 mon inrolled, fold up against each other, to some extent like a pair 



-i- placed face t" face. Often one lobe is larger than, and exceeds the 

 other. This form "i the disc is unusual, and sine.' it prevails in all the 



s[ ii nous (of which there are twenty-three certain and one doubtful case), one 



may fairly assume it to be a constant specific character. So the disc has a 

 much greater diameter in ti-.n than in the other. In the cases which 



I examined, the axis of folding did not, as a rule, hear any definite relation 

 to the line of the two actinopharyngeal grooves. The disc has extremely— 

 unusually— prominent radii, corresponding in number to the tentacles. The 

 ten? usually salmon-coloured, the latter with brown flecks 



ami '.lie radii. The ten ten lender and of medium length, 



and are situated at the extreme margin of the disc in two cycles only ; they 



. when mi y seen, the bases of those of 



the innei eem t>> lie approximately on :i dead level. Sometimes it 



-■■in'- t.-i • ow at tin- expense of others, so ih.it in places 



tin\ found squeezed into a crack between larger ones — they conform 



to the ; b iment, however. Sometimes the tentacles at the 



angles between the two lobes of the die nailer than those between the 



angl n had the total numbei of tei ibout 160. The 



'.1. in this specie- here and there not 



uently ■ □ tie- outside a : m, as if it were the irregular 



month of a large cinclis; sometimes mesenterial filament protrudes, as 

 through a wound In oi lei t" clear this up, I made a very careful examina- 

 tion of the wall ■>!' the greater part of one specimen, removing all ihe 

 mesenteries ami the endoderm. One could then show that the inner surface 

 of the wall revealed a number of mots"; two or three of these com- 



municated by passages with thi r, reaching a pulpy tubercle on which 



they open. i. But others were merely soft ; shallow pits, and did not 



