39 



each tentacle. Half of the pairs are decidedly larger than the others ; 

 the large and small pairs alternate, the former alone being perfect. 

 Longitudinal and parieto-hasilar muscles, as well as reproductive 

 organs occur on all the mesenteries. There is no circular muscle in 

 the column wall. 



Especial interest attaches to this form on account of the discovery 

 among the deep sea actinians obtained by the »Challenger« of two 

 species, named by R. Hertwig who described them^ Ophiodiscus cm- 

 nulatus and O. sulcatus^ which are probably related to Lehrunia. 

 Enclosed in the same piece of cloth as O. annuiatus was a peculiar 

 dendritic structure, evidently coelenterate in its nature, which Hert- 

 wig believes with reason to be a pseudo-tentacle belonging to one of 

 the specimens. All the specimens show evidence of rough treatment, 

 the tentacles being all frayed and torn and the column wall, being 

 rent here and there between the insertions of the mesenteries, and it 

 is very probable that the pseudo-tentacle and its fellows were torn 

 away during the bringing to the surface of the specimens which came 

 from great depths. In shape the pseudo-tentacle differs greatly from 

 that of Lehrunia^ and other differences likewise occur. Thus there 

 were only 48 pairs of mesenteries, of which 24 were destitute of repro- 

 ductive organs and provided with muscles, while the other 24, con- 

 stituting the fourth cycle, were very much reduced in size, forming 

 small folds in the angle between the column wall and the base, and pos- 

 sessing neither muscle or mesenterial filaments, but being gonophoric. 

 A circular muscle imbedded in the mesoglcea of the column wall is pre- 

 sent. The tentacles resemble those of Lehrunia in being inserted on 

 the margin and hanging down over the column. 



Owing to the uncertainty regarding the nature of the pseudo- 

 tentacle of Ophiodiscus Hertwig did not consider it advisable to create 

 a new family for the reception of the genus, but, relying on the nature 

 of the circular muscle, placed it in his family Paractidae. He recogni- 

 zed the possible similarity to Leh'unia as indicated by the pseudo- 

 tentacle and the situation and general characters of the tentacles, but 

 could not decide whether they belonged to the same genus or not, 

 though from the difference in the shape of the pseudo-tentacles it was 

 evident that they were to be considered distinct species. My study of 

 Lehrunia has shown that Opliiodiscus cannot be associated in the same 

 genus with it, the absence in the West Indian form of a circular muscle 

 and of specialized gonophoric mesenteries being sufficient to separate 



2 R. Hertwig, Report on the Actiniaria. Challenger Reports. Zoology. 

 Vol. VI. 1882. 



