v HALAC08TRAGA <-'- 



, are known from the E<x- -m- and Oligocene. The recent Thelphuta, 



Fio. 1024. 

 Xanthopsis Kressenbergensis, v. Meyer. Eocene ; Kressenberg, Bavaria. Male, ventral ami dorsal aspect*, Vfr 



Latr., and Gecarcinus, Leach, occur in the fresh-water Miocene beds of Oeningen 



FIG. 1403. 



Xantho2)sis Bruckmanni, v. Meyer. Eocene; Sonthofen, 

 Bavaria. Ventral view of female, Vj. 



i 104. 



Coeloma mqll, M . K- 1 w. Eocene ; I^verda, 

 [taly. 



and Engelwies in Baden. Archaeoplax, Stimpson, is found in tin- 

 Head, Massachusetts. 



of Gay 



Order 5. EDRIOPHTHALMA. Leach. 

 (Arthrostraca, Burmeister ; Tetradecapoda, Dana.) 



Malacostraca with lateral sessile eyes, usually with seven, more n /' fewer free 



cephalothoracic segments, and an equal 'number of pairs of legs adapted for creeping or 

 swimming. 



Sessile-eyed Crustacea are somewhat rare in the fossil state, and as a rule are 

 imperfectly preserved ; this, taken in connection with the fact that the clarification is 

 largely based upon the minute mouth-parts, makes the identification and systematic 

 arrangement very difficult and often impossible. 



