INVERTEBKATE ANIMALS. 71 



ing, ecdysis, of the higher Crustacea is still open to 

 discussion. 



Estimated number of species : recent, 3 (M. Edwards) ; 

 British, 1. 



IT Example of common Lobster, and of the gigan- 

 tic American variety. 



Upper Compartnu'Tit. 



Lobster articulated, so as to exhibit the segments 

 with their appendages. 



Group 171.— Family PALINURIDiE. The Spiny-lobsters 

 are undoubtedly amongst the most handsome of the 

 Macroura; but the group is chiefly interesting from 

 the fact that the Glassy-crabs, Phi/llosoma, till recently 

 supposed to be included in the Stomapoda, are now 

 recognised as larval forms of the PaUnuridce. In 

 Astacus and Homarus, the young, from the time when 

 they are very small, are said closely to resemble the 

 adult. If this be true, the affinity between the Lobsters 

 and the Spiny-lobsters is probably simply a mor- 

 phological one, and points of great interest may be 

 expected to occur during future investigations of the 

 phylogeny of the Spiny-lobsters. The species are widely 

 distributed, and are found on rocky coasts. 

 Estimated number of species: recent, 13; British, 1. 



11 Examples of Palinurus guttatus, P. Lalandii, P. 

 longimanus, &c., and of Phijllosoina. 



Group 172.— Families SCYLLARID^ and GAL ATHEID^E. 

 The Broad-lobsters, Scyllaridce, derive much of the pecu- 

 liarity of their form from an extaordinary modification 

 of the outer pair of antennae, which in this family are 

 developed into broad flat plates, sometimes strongly 



