Two of these forms are new; two have also been observed in the North, and one is distributed extensively over the earth.
The distinguishing characters of the seven new genera collected in the course of the voyage, viz. Anaulus, Asteromphalus, Chætoceros, Halionyx, Hemiaulus, Hemizoster and Triaulacias are given in pages 19, 20, and 21, of Professor Ehrenberg's communication to the Academy of Science at Berlin: and those of the seventy-one new species in eight following pages, to which I must refer the enquiring naturalist for further information.
APPENDIX, No. VI.
LETTER FROM LIEUT. CHARLES WILKES, COMMANDING UNITED STATES EXPLORING EXPEDITION, TO CAPTAIN JAMES C. ROSS, H.B.M.S. EREBUS.
"U.S. Flag Ship Vincennes, New Zealand,
"Bay of Islands, 5th April, 1840.
"My dear Sir,
"I need not tell you how much I feel interested in your cruise. From the interest you took in the outfit of our expedition, I am sure you well know the interest it excites, and how much this feeling is heightened by a knowledge on my part of what you have undertaken, and have to go through. This prompts me to a desire to be useful to you if possible, and to give you my experience of the last season among the ice, whither you are bound.
"Your cruise will be an arduous one, no matter how you may be enlightened in your course; but you have so much knowledge of the ice, and the manner of treating it, that it appears almost presumptuous in me to sit down to give you any hints relative to it. But, believing as I do that the ice of the antarctic is of a totally different character from that of the arctic, I venture to offer you a few
