﻿April, 1857.] 



ELLIOTT SOCIETY. 



209 



they very nearly touch each other laterally, and stretch very 

 nearly from top to bottom of the disk-cavity, thus occupying al- 

 most the whole inner surface of the bell. When viewed from 

 above, their unyielding structure gives the disk a quadrate out- 

 line, and viewed in profile they appear as large circular shields, 

 especially when at the death of the animal they assume a marked 

 white coloration. The proboscidian elongation . of the disk is 

 rather slender below, increasing in diameter rapidly above the 

 digestive cavity; the oral leaflets not so long as in Eutima mira, 

 and the four extensile tentacula, I do not recollect ever to have 

 seen stretched more than twice, occasionally, perhaps, thrice the 

 length of the trunk, including the height of the disk. The upper 

 surface of the umbrella is usually very spherical and smooth, some- 

 times, however, the outline viewed in profile becomes somewhat 

 emarginate in its descent from the vertex to the tentacular rim. 



This species is evidently gregarious, great numbers being found 

 together in nearly every instance when I have found it at all. It 

 is bold and rapid in its movements and very rapacious. I have 

 seen one of this species so extremely diaphanous as to make the 

 impression of nothing but a set of outlines — sieze upon a small 

 fish fully thrice as large as itself, and securing itself by spreading 

 out its lips upon it, making them act as suckers, and then entang- 

 ling about the poor animal its four long tentacula, hang on in this 

 manner despite the violent struggles of the fish, which alarmed 

 swam violently about the jar, until at last apparently from sheer 

 exhaustion, it was evident he was dying. At last changing color, 

 the fish turned over on his side and expired. 



I have found specimens of this species from time to time during 

 five months of summer, beginning with the first week in June 

 and ending with the last of October. It may be considered one 

 of the most common of our species. 



V. AEGIN1DJ2. 



In the present state of our knowledge this is the most aberrant 

 and distinctly characterized group of Hydroidea. It is at the 

 same time the lowest in type, both as to structure and develop- 

 ment. The general form for the most part is flat and discoid, 

 sometimes thickening into a more hemispherical shape. The 

 mouth is usually simple, the digestive cavity broad, flat, and 

 imbedded in the disk. Radiate tubes rudimentary or altogether 

 wanting. No marginal canal. Sexual organs so far as known, 



