THE ENTOMOLOGIST. 638 



following year, 1816, in his 'Animaux sans Vevtebres,' 

 pp. 64 and 1 16, and an admirably clear figure, accompanied 

 by details, is given in plate viii. Limulus is again described 

 by Latreille in 1825, at p. 304 of his 'Families Naturelles;" 

 a second time, by the same author, in 1829, at p. 184 of the 

 fourth volume of the second edition of the 'Regno Animal;' 

 and a third time in 1 831, at p. 442, of the same author's, ' Cours 

 d'Entomologie.' The first and third of these works are 

 little known, and never cited on this side the Channel, nor 

 have they — even in the native country of their illustrious 

 author — the reputation they undoubtedly deserve. 



The whole of Savigny's profound remarks are based on the 

 theory that all the articulated animals possess essentially the 

 same organs of manducation and locomotion, but that these 

 organs are vastly and wonderfully modified : this theory is 

 fully explained, and is clearly rendered feasible, if not abso- 

 lutely established, in the investigation of the seven classes of 

 hexapod insects. In my 'Grammar of Entomology' and 

 'Familiar Introduction' I have fully adopted Savigny's 

 theory ; but now that I come to consider the king crab, and 

 read its character in Nature's book, even with Savigny's 

 explanations, I feel great difficulty in accepting the latter as 

 satisfactory. The difficulty becomes still greater when we 

 introduce the crab, the lobster, and that strange being Apus 

 cancriformis, into consideration. Hence I conclude that the 

 theory may without hesitation be accepted, so far as the 

 hexapods are concerned, but that it requires much care in 

 extending it to the apiropods. 



Turning the animal on its stomach we see at once that its 

 circumscription somewhat resembles that of a boy's kite, the 

 anterior margin being semicircular, and the lateral margins 

 oblique and connivent. This kite-shaped figure is covered by 

 a hard and polished shell or shield, transversely divided into 

 three parts or sections, united together by powerful hinges, 

 which stiffen and become almost immoveable after death. 

 The first section (1) is broad and semicircular in front, 

 produced into two points behind ; nearly in the n)iddle we 

 observe a raised portion, and on this are three ridges or 

 keels ; one of them is shorter than the others, and uiedio- 

 dorsal; the others lateral; the medio-dorsal keel has two 

 ocelli, or simple eyes, at its anterior extremity, one on each 



