462 Verrill, Notes on Madiata. 



several of which originate from each radiating chamber or ambulacral 

 space, and are therefore arranged in simple radiating lines, or in radi- 

 ating groups when more than one series arise from the same chamber. 

 These false tentacles increase in size from the centre to the margin of 

 the disk. The disk is usually broad and widely expanded, but gene- 

 rally capable of complete contraction. 



This subfamily includes the true genus, Dlscosomal^Qwok. {? Miconlea 

 jy. and M.), excluding many forms wrongly referred to it by various 

 authors ;* Somactis and Stejyhanactis Verrill ;f and apparently Echin- 

 aotis E. and H., Corynactis Allman, Aureliania Gosse, and Gapnea 

 Forbes. But most of the descriptions and figures of these genera are 

 insufficient to determine with certainty whether the " tentacles " ori- 

 ginate each from a distinct chamber or not. For the three genera last 

 mentioned Gosse has formed the family, CapneadcB, but he does not 

 refer to this character, and regards all the disk-tubercles as true ten- 

 tacles. 



Subfamily, Phyllactin.e Edw. and Haime. 



Metridium (genus) Ehrenberg, 1834, {non Oken); Dana, Zoopli., p. 150, 1846. 

 PhyllactinoR {^wM-AvaMj) Edw. and Haime, Corall., i, p. 291, 1857; VerrOl {pars), 

 Mem. Boston Soc. Nat. Hist., i, p. 15, 1863. 



Column usually rather low and broad, its surface generally bearing 

 verrucae or suckers, sometimes nearly smooth. Disk broad, the tenta- 

 cles placed considerably within its margin. The branchiform appen- 

 dages either form a circle just within the margin and outside of the 

 tentacles, Oulactis • are mingled with the tentacles, Hhodactis ; or 

 cover the buccal area within the circle of tentacles, Actinotryx; or are 

 placed both within and outside of the circle of tentacles, Amphiactis 

 V.| These organs diifer greatly in number, size, and form in the dif- 

 ferent genera, as well as in position. 



The genus, Aulaetinia, which I formerly referred to this subfamily, 

 on account of the lobed, sub-marginal, branchiform pai>illge, appears 

 to belong rather with the Bunoditui\ The same is true of Oulactis 

 granulifera (Les. sp.) E. and H., and Anthopleura Krebsii D. and M. 

 It was on account of these and other similar forms that the group 

 was formerly made a subfamily of Actlnidw by me, but in that fam- 

 ily the branchiform appendages are really lateral organs, originating 

 from or below the margin. 



* Discosomus was used among Reptiles by Oken in 1816, and Discosoma among 

 Arachnida in 1830 by Perty. Ehrenberg has proposed to subtitute the name Disco- 

 stoma, for Luckart's genus. 



f Proceedings Essex Institute, vol. vi. | Proc. Essex Institute, vol. vi. 



