﻿April, 1857.] 



ELLIOTT SOCIETY. 



207 



trace the tubes with certainty. When contracted, and this may 

 be a generic character, there is scarcely any longitudinal shorten- 

 ing of the body, but the contraction produces deep longitudinal 

 furrows which proceed from the bell-margin up to the thickened 

 basis of the digestive trunk. The largest of these specimens was 

 not quite the tenth of an inch in height. 



I did not ascertain any facts with regard to its embryological 

 history. 



• The three specimens of this species were taken in the last week 

 of January, on the same day. Another taken 22d of May, did not 

 throw any further light upon the obscure characters of the species. 



IV. GERY0NID.32. 



The form is, generally, more or less that of an umbrella, with a 

 long peduncle which, according to Gegenbaur, contains in Geryo- 

 nia, proper, a large cavity, interposed between the digestive cavity, 

 proper, (which as in Tima and Eutima is terminal,) and the origin 

 of the radiate tubes. This is probably homologous with the 

 cavity of the slender pedicle, which in Aglaura supports the large 

 digestive organ. In Liriope, I have not observed any such cavity. 

 The mouth is provided with labial tentacula. The number of radi- 

 ate tubes vary, but it seems to be always a multiple of two, rather 

 than of four. The marginal canal, according to the author just 

 cited, gives off in Geryonia proper a number of blind diverticula, 

 which penetrate the disk centripetally, and are of various lengths. 

 The sexual organs are large, oval, circular, or cordate sinuses in 

 the course of the radiate tubes. They are flat and do not bulge 

 out into the cavity of the disk, as is more or less the case with the 

 foregoing genera. Their number probably is uniform with that 

 of the radiate tubes. The tentacula exceed the radiate tubes in 

 their number, which, however, appears to be still a multiple of two, 

 rather than of four. They are usually of two sorts. The number 

 of marginal capsules is the same as that of the tentacula, with 

 whose bases they are connected. This connection in Liriope is, 

 as in Obelia, asymmetrical ; and probably closer inspection would 

 show it to be so in all cases. In Liriope occurs a singular instance 

 of a double marginal capsule, which is also connected in an unu- 

 sual manner with the outer surface of the disk. 



The development of the Medusae of this group, which are by no 

 means uncommon, has never yet been observed. This suggests 

 the probability that it is a direct metamorphosis from a free larva. 



