48 MEMOIR III. 



is much depressed, is composed of nine segments; of these, 

 the anterior is largest, constitutes the clypeus, and presents 

 towards its middle part the appearance of a pair of proxi- 

 mate eyes; the posterior segments diminish in width as they 

 approach the opposite end or tail, and the last of them is 

 terminated hy two elliptic fins or scales, setaceous on their 

 outer edge and having a central longitudinal nerve or rib. 

 The Sapphirina swims in all directions with apparent ease 

 by the motion of its tail, and often darts away by some 

 sudden effort of its concealed members. There can be no 

 doubt of this animal belonging to the Monoculi of Linnseus, 

 and most probably to the same family with Cyclops, a re- 

 lationship which \inll be more apparent, when we become 

 acquainted with the structure of a nondescript member of it 

 lately detected in our own seas, and which it is intended to 

 develope in a succeeding Memoir. The geographical distri- 

 bution of the Sapphirina appears to be limited to the seas 

 situated to the north and west of a line drawn from the 

 Cape of Good Hope to the southern extremity of the Island 

 of Ceylon. 



There is yet another of these luminous Phenomena which 

 merits a moments consideration, viz. that which in violent 

 storms at sea, makes it appearance in a luminous patch 

 or ring upon the masts and on the windward yard-arms, 

 gradually mounting up the former as the storm increases in 

 violence ; this appearance most probably results from the 

 minute luminous animals being carried up and lodged there 

 by the spray of the sea, which, while it continually furnishes 

 a fresh supply and excitement, gains gradually a higher 

 range, until the storm is at its height. Having only sailed 

 in large Vessels, I have frequently observed an appearance 

 of this kind on the lower masts and windward rigging ; this 

 has in all likelihood been often confounded with the Fire 

 of St. Elmo, which would seem to be a purely electrical 

 phenomenon, and is described as resembling a radiant star or 

 flame playing about the very summits of the masts. 



