12 FOSSIL MALACOSTRACOUS CRUSTACEA. 



legs, Professor M'Coy gave the name of Notopocorystes* was long involved in considerable 

 confusion, arising principally from the total ignorance of the structure of this class of 

 animals on the part of the discoverer of two of the species of which it is composed. In 

 the ' Illustrations of the Geology of Sussex, 'f and subsequently in the ' Geology of the 

 South-East of England,'! the late Dr. Mantell announced, and in the ' Medals of Creation '$ 

 imperfectly described, a few Crustaceans occurring respectively in the Gault of Kent and 

 Sussex and the upper Greensand of Lyme Regis and Cambridge. In the first instance 

 he submitted the specimens to Dr. Leach, who stated their real or supposed affinity to 

 existing genera. His very brief observations were accompanied in each case by a single 

 phrase on the part of the author of the works above cited, which afforded not the slightest 

 indication as to the true character of the species, the few details given being either nuga- 

 tory or absurd ; || whilst the figures in the two earliest of the works mentioned are scarcely 

 recognisable as representations of the creatures to which they refer. The true relation of 

 Mantell's two species of Corystida? was, however, at once seized upon by Leach, who 

 considered one of them as " intimately related to the typical genus Corystes," and the 

 other as " allied to a new Indian genus of the same family." I shall presently show how 

 correct was this general conclusion. 



Taking up the subject at this point, Professor M'Coy gave a full and correct descrip- 

 tion of Corystes Stokesii of Mantell under the name of Notopocorystes ManteUi. Por 

 what reason he changed the specific name does not appear, as Mantell's name was pub- 

 lished four years before M'Coy 's, and the latter suggests that they might be identical. 

 The second species is not even alluded to in M'Coy 's paper, and he erroneously considers 

 as a species of this genus the Orythia Bechei of Deslongchamps, which is designated by 

 Leach as " a new genus allied to Areania," and named by Mantell Areania BucUandil* 

 There are no grounds for considering it as generically allied to M'Coy's Notopocorystes, 

 and its relation to Areania is obviously still more remote. A 



In the present work I have the opportunity of describing a third and very beautiful 

 species of the genus now under consideration, P. Normani, from the Chalk Marl at 

 Ventnor, in the Isle of Wight. 



In the year 1854 Mr. M'Coy published in the ' Annals of Natural History' a descrip- 

 tion, with figures, of a very interesting Crustacean, which he referred to the same genus, 

 under the name of Notopocorystes Carted, but this I have found it necessary to consider as 

 a new generic form, under the name Eiicorystes. 



* "Etym., vwrot dorsum, irovs pes, and Corystes." M'Coy, 'Ann. Nat. Hist.,' 1819, p. 169. 



t T. xxxix, figs. 9, 10, 15, 16. 



X P- 109, fig. 2. 



§ P. 532, figs. 2, 3. 



|| For instance, as one distinctive specific mark of a Decapod species, it is stated that " there are three 

 or four le^s on each side !" 



^j 'Medals of Creation,* p. 534. 'Geol. S.E. of Eng.,' p. 169, fig. 3. It is Necrocarcinus Bechii 

 of the present work. 



