ON THE SHETLAND CRUSTACEA, TUNICATA, ETC. 325 



sight, looking over the yacht's side, was a thing never to be forgotten. 

 The sea was swarming with myriads of the Pliysophora, Diphyes, Cydippe, 

 and allies, Cyanea, Aurelia, &c., and long chains of Salpa runci- 

 nata. Among the animals observed that evening was a Medusa (using 

 that word in a class sense) which was quite unlike any genus that I am 

 acquainted with, a little flat plate, about tho size of a threepenny piece, 

 with very numerous long tentacles round its edge, the whole animal 

 perfectly transparent and colourless. 



NAKED-EYED MEDUSA. 



Although the following species ought to be incorporated with and inserted 

 in their proper places among the preceding Hydrozoa, yet our knowledge 

 being at present confined to the gonosome, it is not possible to allocate them 

 with any degree of precision. I have thought it better therefore to keep 

 them together here, leaving future discoverers, who shall become acquainted 

 with the trophosomes, to assign them their respective places. My own 

 time in Shetland was too much taken up with other animals to allow me to 

 study these Medusoids. The following list contains the species observed in 

 Shetland by Forbes, as recorded in his ' British Naked-eyed Medusae ;' but I 

 have arranged them more in accordance with our present state of knowledge, 

 throwing them into the families and genera to which they are referred by 

 Prof. L. Agassiz in his * Contributions to the Natural History of the United 

 States,' vol. iv. 1862, and by his son, Alexander Agassiz, in his ' Illustrated 

 Catalogue of North American Acalephae,' 1865. 



Order THECAPHORA, Hincks. 



Fam. OCEANID^;, Esch. 



Genus PLATYPYXIS. 



Thaumantlas ceronautica, Forbes. " Off Bressay, and in Hamna Voe in 

 Papa" (Forbes). 



maculata, Forbes. " Sound of Bressay, but not plentiful " (Forbes). 



Not hitherto observed elsewhere. 



globosa, Forbes. " Very abundant in the harbours on both sides of the 

 Shetland Isles " (Forbes). Not as yet noticed elsewhere. 



melanops, Forbes. " Has hitherto occurred only in the Zetland seas, 



and is not very common there " (Forbes). 



L. Agassiz considers the above four species to be referable to Pla- 

 typyxis, L. Agass., or the closely allied genera Clytia, Lamx., or 

 Wriyhtia, L. Agass. ; but the younger Agassiz subsequently writes (Cat. 

 North Amer. Acalephas, p. 103), " may not the T. gibbosa of Forbes be a 

 young Halopsis? They resemble the young of this species (Halopsis 

 cruciata, A. Agass.) ; also T. ylobosa, and perhaps T. pilosella" 



Genus OCEANIA, Per. & Les. (restricted). 



Thaumantias JiemispTwerica, Forbes. " Zetland, where they abound in the bays 

 and harbours " (E. F.). This species is considered by L. A. to be synony- 

 mous with Oceania phosphorica, Peron & Les. and the T. inconspicua, T. 

 lineata, T. punctata, T. pileata, and T. Sarnica are said to be probably 

 different stages of growth only of T. hemisphcerica. 



lineata, Forbes. " Taken in the Zetland seas in 1846, but not found 



common" (E. F.). 



convexa, Forbes. " A very common species in the Zetland seas " (E. F.). 



" May be a distinct species " (L. A.). 



