70 Mr. Wcstwood on Arcturus, 



essential characters with tlie Isopoda, appears to me to form the con- 

 necting link between that order and the Lcemodipoda . 



The genus was established by Latreille in the 2nd edition of the 

 R'egne Animal*, published in 1829 (having been indicated by name 

 only in the Families Naturelles, published in 1825). Its characters 

 were derived solely from the legs ; and it would appear that a mutilated 

 specimen had been examined, as the form of the fourth pair of legs 

 is not noticed. Latreille adds : " Sous le rapport de la longueur des 

 antennes et de la forme du corps ils se rapprochent des Stenosomes." 

 Latreille also states, that he had seen only a single species {Arcturus 

 tuberculatus) , which had been brought from the Northern Ocean in 

 one of those British expeditions to the polar regions, which have 

 not only rendered immortal those intrepid heroes by whom, in spite 

 of the most fearful dangers, they have been accomplished, but have 

 also conferred an additional and distinguishing honour upon the 

 national character of our country, which it is difficult to reflect upon 

 without a glow of enthusiasm or a burst of patriotic feeling. 



The situation assigned to this genus by Latreille was in the midst 

 of the Isopoda, between the genera Stenosoma and Asellus. 



No description was given by Latreille of the species, but from its 

 name and locality it seems to me to be identical with the Idotea 

 BaJJini of Sabine, figured and described in Captain Parry's Voyage 

 of Discovery, published four years previousl}^ (1821), with which 

 liatreille does not ajjpear to have been acquainted. 



In Sowerby's British Miscellany, however, we find several figures 

 of a very remarkable insect, named Oniscus longicornis, which, al- 

 though disagreeing in several material points with the Idotea Bajffini, 

 must evidently be considered to belong to the same genus ; and it 

 is remarkable that these figures should have been overlooked by 

 crustaceologistsf. For several specimens of this insect I am indebted 

 to Dr. Johnston, the celebrated zoologist of Berwick-upon-Tweed, by 

 whom they were collected in Berwick Bay ; and, as they were pre- 

 served in spirits, I have been enabled to give a complete series of 

 figures illustrative of the structure of the genus. As this insect, 

 however, possesses characters of sufficient weight to warrant its 



* Mr. Curtis in 1830 gave the same name to a genus of Moths, which must con- 

 sequently be rejected : perhaps he will himself take an early opportunity to re-name 

 it, notwithstanding his recently expressed determination not to throw down any 

 generic name published with characters, although such name may have been pre- 

 viously employed. 



t Since this memoir was read, I have learned that Dr. Johnston published a de- 

 scription of this animal in Jameson's Edinb. Phil. Journ., vol. xiii. 1825, p. 219, 

 under the name of Leacia lacertosa. In this memoir the structure of the trophi and 

 of the internal branchial plates was not noticed, the large middle segment is stated 



I 



