22 



IV. — Observations on certain points in the Anatomy of a species of 

 Thaumantias. By George Busk, Esq., F.L.S., President of 

 the Society. 



(Read March 28th, 1849.) 



The species of Thaumantias forming the subject of this paper, 

 most nearly resembles T. inconspicua or T. sarnica, Forbes, from 

 both of which, however, it appears to differ in the shape of the repro- 

 ductive glands, which are not linear, as described in both those 

 species, but short and ovate. From the former species, also, it dif- 

 fers in the absence of colour in the tentacular bulbs. The specific 

 name, therefore, is left undetermined ; but this is of the less conse- 

 quence, as the subject of this paper is merely to describe certain 

 points of anatomical structure presented by this species, in common 

 with many others ; and in a modified form, perhaps, by all its con- 

 geners. 



It was very abundant last autumn in the sea between Portsmouth 

 and the Isle of Wight, a locality apparently very favourable to the 

 smaller and more delicate species of gymnophthalmatous Medusa. 



This Medusa is about three-fourths of an inch in diameter, and 

 the disk is rather depressed ; varying, however, a good deal in this 

 respect (fig. 1, a, b). It is perfectly transparent and colourless in all 

 parts. The subumbrella ascends to about three-fourths of the height 

 of the umbrella. The margin of the disk is furnished interiorly with 

 a pretty wide velum, and supports from eight to thirty-two tentacles 

 according to the age of the animal. The age may probably be cor- 

 rectly deduced, not merely from difference in size, but from the 

 greater or less completeness in the development of the reproductive 

 glands. The peduncle contains a simple cavity, into the base of 

 which the four gastro-vascular canals seem to open directly. The 

 margin of the lips of the peduncle is entire, and when the organ is 

 contracted, this part and the greater portion of the peduncle itself is 

 thrown into four angular folds (fig. 2). The substance of the pedun- 

 cle and lips is composed of a fine cellular tissue, and the margin is 

 slightly thickened and beset with filiferous vesicles, as indeed in a 

 less degree is the whole surface of the peduncle. Four principal 



