British Tenlhredos. — New Species of Usnea. 1 53 



BRITISH TENTHREDOS. 



A young entomologist would esteem it a great favour if any 

 of our correspondents would favour him, through the medium 

 of the Philosophical Magazine, with the specific naines and 

 characters of the different British species of Tenthredos, and 

 at the same time mention the plants, shrubs, or trees, on which 

 the larvce of each feed. 



NEW SPECIES OF USNEA, FROM NEW SOUTH SHETI-AND. 



In Silliman's American Journal of Science and Arts, for 

 January last, (vol. vi. No. I.) p. 104', is a letter from Dr. S. L. 

 Mitchill of New York to Dr. Torrey of the same place, re- 

 specting a new Cryptogamic Plant found by Capt. Napier 

 growing on the top of a rock, from which the snow had melted 

 off, in an island of the group called New South Shetland. It 

 would appear that this plant, and a dwarfish grass of which a 

 few tufts were seen by Capt. Mackay, are the only vegetable 

 productions of those islands ; for Dr. Mitchill was informed, 

 that " notwithstanding the frequency of lava and volcanic slag, 

 and the occasional eruption of smoke from the earth in different 

 places, the surface was generally covered with ice and snow, 

 even during the southern summer;" and that " there is not a 

 shrub nor a tree to be seen, nor any appearance of verdure 

 to cheer the prospect." — The following is Dr. Torrey's ac- 

 count of the plant in question : 



" The specimens presented to me by Dr. Mitchill, evidently 

 belong to a species of Lichen. Several of them were covered 

 with small tubercles very much resembling the fruit of Roccella, 

 which, with the habitat of the plant, induced me to refer it to 

 that genus. On a closer examination, however, I have no 

 doubt of its being a species of Usnea without the proper fruit, 

 merely having the cephalodia which are not uncommon in 

 U. Jlorida, &c. 



It has the centre hyaline thread, so constant and important 

 a character in this genus. According to Acharius, all the 

 Usneae are found exclusively on trees : so that this species, 

 whicli grows on rocks, appears to form an exception to all the 

 rest. In the Flore Fran^aise, however, the U.Jlorida is said to 

 occur sometimes on rocks, and the U. articulata on the ground. 

 The present species does not appear to be described in tlie 

 Synopsis Mcthodica Lichenum of Acharius ; I have therefore 

 considered it as a new one, and have called it U.fasciata. 



" UHiiZAjasciata. 

 " U. thallo pendulo scabriusculo tereti glauco virescente 

 ramosissimo, ramis rectis nigro-fasciatis quasi articulatis, 

 ramulis ultimis capillaceo-attenuatis, fibrillis lateralibus nul- 

 lis, cephalodiis sparsis hemisphaericis atris." 



LJ 2 Desciut. — 



