58 



Guide fo Crnsiacca. 



Tablc-cLisu 

 Xo. 11. 



The ];ii-vac of ilic Loricala arc very unlike lliose of llie related 

 groups, and are remarkable for their extremely liattened forui and 

 glassy transparency, and for the large size which they sometimes 

 attain. They were formerly regarded as adult and independent 

 species of Crustacea, and received the generic name of 

 PJiyllosoina (Fig. 37). 



Eepresentatives of the extinct family Glijpliaeidac are found 

 fossil in rocks of Mesozoic age, from the Trias onwards. In some 



Fig. 37. 



The " PlnjUosoDia " larva of the common Spiny Lobster, much enhirgctl. 

 (After J. T. Cunningham.) 



characters, such as the possession of a scale or exopodite on the 

 antenna, and sometimes in having true chelae, they are much 

 more primitive than the existing Loricata. A drawing of Crli/j)]i(ic(i 

 regie.]/ ana from the Jurassic of France is exhibited. 



In the Tribe Eeyonidea the first four, and sometimes all five, 

 pairs of legs are provided witli chelae. Special interest attaches to 

 this tribe on account of its geological antiquity. Fossil forms, not 

 very different from those now living, are found in rocks of 

 Mesozoic age, from the Trias onward. 



