Crustacea — Entomostraoa. 



78 



intermediate position between the Phtllgpoda. and the higher GALLEBY 

 Malacostraca (such as Mysis and Byastylis), though they certainly 

 appear to be more nearly related to the former (the Phyllopods). i2-14 

 The living Nehalia is a small marine crustacean, but the giant Table 

 pod-shrimps, such as Ceratiocaris Ludensis, from the Silurian of 8o_85^ 

 Ludlow, attained a length of 2 feet. Other Palaeozoic examples 

 are Jsoxys Chilhoweana (Walcott), from the Lower Cambrian ; 

 Symenocaris vermicauda, from the Upper Cambrian ; and Ceratiocaris 

 papilio (see Fig. 121, ^Z), from the Upper Silurian of Lanark. There 

 are also Bithyrocaris, Aptychopsis, and many other genera ranging 

 from the Cambrian to the Carboniferous period ; they have not 

 been met with in later rocks. 



Fig. 121. — Entomostracous Crustacea. 

 Phyllocarida. 



1. Ce7'atiocaris papilio, Salter. Upper Silurian : Lesmahagow. (T^^ij- nat. size.) 



2. Nebalia hipes, Fabr. (living) ; half of carapace removed to show the body 



and appendages. 



Phyllopoda. 



3. Lepidurus Angasii, Baird. a, dorsal aspect (adult) ; b, ventral aspect. 



4. Larva of Apus cancriformis, Schsefi'er. 



5. Branchipus [Cheirocephalus) stagnalis, Milne-Edw. a, adult female ; 



b, c, larvae. 



6. Larva of Artemia salina. Leach. 



5. — Trilobita. The Trilobites form a very large but extinct order 

 of Entomostraca, the exact position of which was for a long time 

 a matter of doubt, as no appendages had ever been found with 

 any of them. By the recent discoveries made in North America,* 



> E. Billings in 1870; C. D. Walcott in 1881; W. D. Matthew in 1893; 

 C. E. Beecher in 1894. 



