REPORT ON ZOOLOGY. 193 



Squilla. The Amphipoda consist principally of such Crustacea 

 as were referred bj'^ Fabricius to his genus Gammarus. The 

 Isopoda answer to the Onisci of Linnaeus. The Amphipoda 

 and Isopoda together constitute Dr. Leach's second legion, 

 Edriophthalma. Latreiile's fifth order, Branchiopoda, includes 

 the Entomostraca of Miiller and Leach, referred by Linnaeus 

 to his genus Monoculus *. 



Since the appearance of the R^gne Animal, other naturalists 

 have occupied themselves with this class. Latreille has also 

 modified his own arrangement in some subsequent publications, 

 availing himself of many valuable researches on the part of differ- 

 ent individuals, relating more particularly to the Entomostraca. 



In the Families Naturelles, published in 1825, we find the 

 Crustacea divided primarily into the two sections of Maxillosa 

 and Edentata. The former comprises, in addition to the old 

 orders Decapoda, Stomapoda, Amphipoda, and Isopoda, three 

 new orders, — one, Lcemodipoda, for the reception of the Isopodes 

 Cystihranches oi the R^gne Animal, placed between the Stoma- 

 poda and Amphipoda ; the other two, Lophyropoda and Phyllo- 

 joorfa, taken out of the old order 5rancAiopoJa,andterminatingthe 

 first division. The second section contains the remainder of the 

 Branchiopoda arranged under the two new orders Xyphosura 

 and Siphonostoma. Thus we have the Entomostraca, which 

 before constituted but one order, here forming four. Latreille 

 in his last work, Cours d' Entomologie, has increased the orders 

 still further. He has adopted three other new ones, called Dicla- 

 dopa, Ostrapoda, and Trilobita. The first of these, inserted 

 between the Isopoda and Lophyropoda, includes the genera 

 Nebalia, Pontia, Condylura, and Cuma. The second, insti- 

 tuted by Straus, comprises the genera Cypris and Cytherea, and 

 is placed between the Lophyropoda and Phyllopoda. The third, 

 adopted for the fossil Trilohites, forms the last order in his first 

 division of Maxillosa. In other respects his system is the same 

 as that in the Families Naturelles. 



The same year as that in which the Fam. Nat. of Latreille ap- 

 peared, Desmarest published his Consideratio^is Generales sur 

 la Classe des Crustac^s. In this work, which is one of consider- 

 able merit as well as utility f, we have the systems of Latreille 

 and Leach in some measure combined. Thus, the Malacostraca 



• The above arrangement by Latreille was adopted, with some slight modi- 

 fications, by Lamarck in the 5th vol. of his Hist. Nat. des An. sans Vert. 



\ M. Desmarest was the first to draw the attention of naturalists to the dif- 

 ferent regions marked out on the upper surface of the carapace in the Decapoda 

 Brachyura, and to show their exact accordance with the internal organs which 

 they respectively cover. 



1834. a 



