Diana a, Bairdxx. 321 



coat forms two loose folds around the circumference, from the 

 innermost of which the tentacula arise ; and the inner coat is 

 probably a continuation of the outer reflected upwards ; but it 

 is not a simple membrane, since several laminae can be per- 

 ceived to cross the body. The white crucial bands adhere to 

 this inner envelope : they are not muscular, but very probably 

 belong to the generative system. I consider the plumose 

 processes at the oral aperture as subservient to respiration, 

 partly because of their position, and partly because of their 

 folded structure; intended, as it appears to me, to expose the 

 largest possible surface to the action of the water. 



This Medusa is a luminous species. It gives out a copious 

 light of a whitish colour when the water in which it swims is 

 agitated, or when it comes into contact with foreign bodies. 

 In the possession of this wonderful property it resembles the 

 Medusa hemisphae'rica, described and figured by Dr. Macart- 

 ney in the Philosophical Transactions for 1810, p. 267.; but 

 differs otherwise in too many particulars to permit us to con- 

 sider it as the same species. If the readers of this Magazine 

 will turn to the figure of the Medusa hemisphae'rica, given 

 in Vol. III. p. 313. fig. 82. <?, they will perceive that our 

 animal is vastly larger ; has much fewer tentacula pendent 

 from its circumference; has a more produced peduncle, which, 

 instead of being divided into four equal " tentacula, covered 

 with little cups or suckers, like those on the tentacula of the 

 cuttlefish," is not divided at all, but provided with plumose 

 appendages. With these differences I think myself justified in 

 describing it as a distinct species, which I have taken the liberty 

 of naming in commemoration of my friend Mr. William 

 Baird, surgeon to the Berwickshire East Indiaman, and the 

 author of several interesting papers in this Magazine [Vol. II. 

 p. 208., Vol. III. p. 308., Vol. IV. p. 475. 500.J, two of which 

 are descriptive of luminous animals: and Mr. Baird deserves 

 the compliment the more, as, in fact, one of the Medusa de- 

 scribed by him, but not named, appears to be this species in 

 an early stage of its existence, for it was only about the size 

 of a small pin's head. 



The character of the species may be thus given : — 



1. D. hemisphae'rica. — Hemispherical, crossed in an arched 

 manner with four opake lines; margin of the umbella undivided, 

 surrounded internally by a row of pale brown spots, and nume- 

 rous small tentacula; central process divided into four segments 

 covered with suckers. Medusa hemisphae'rica, Macartney 

 in Phil. Trans. 1810, part ii. p. 267. tab. xv. fig. 5,6.; 

 Loudon's Mag. Nat. Hist., vol. iii. p. 313. fig. 82. e. Geryonza 

 hemisphae'rica, Flem. Brit. Anim. 500. — Hah. Coasts of 



Vol. VI. — No. 34. y 



