INTROUUCriDN. VI I 



EuKYi'TJUiiuA. — The Eukypteuida, like the Thilobita, are an extinct 

 order. They were represented in Devonian and Silurian times by g;enera 

 which attained a length of from 5 to 6 feet. They were nearly related to 

 the King-Crabs in structure, but differed in their development as do the 

 Lobsters from the Crabs at the present day — the XipnosuRA representing 

 the Brachyuran, and the EuRrPTERiDA the Macruran tj'pe. 



Phyllopoda. — The Phyllopoda arc represented from the Middle Cam- 

 brian to the Tertiary period by many genera. Large extinct fonns, closely 

 resembling the little modern Nehalia Inpes, were abundant in the Upper 

 Silurian of Ludlow and Lanark. They are represented today by species 

 in fresh water, brackish water, salt water, and highly saline salterns and 

 lakes. 



OsTRACODA. — The Bivalved Entomostraca included in this order are 

 largely represented throughout the entire scries of stratified rocks, from 

 the Lower Cambrian to the present day ; they are equally well represented 

 in a recent state. They not unfrequently (as in the Cjipris shales of the 

 Wealdcn) make up entire strata with their accumulated valves. 



CiRRiPEDiA. (rt) Balanid.!). — The oldest fossil sessile Cirripede is the 

 Pijr(joina cretacea, H. Woodw., from the Upper Chalk of Norwich. 



(6) LEPADiDiE. — The oldest known pedunculated Cirripede is the Turri- 

 lepas Wnyhtil, H. Woodw., from the Upper Silurian of Dudley. None 

 have been met with lower than the Lias, except Tun-ilepas ; but from the 

 Lias upwards, sessile forms are well represented. 



The group is abundant and cosmopolitan in aU the seas of the world, 

 parasitic on all objects, living and dead. 



The subjoined Table (p. viii) gives the number of genera, species, and 

 varieties belonging to each order and suborder in the class Crustacea. 



HENRY WOODWARD. 



Department, of Geology, 

 December 22, 187l). 



