CRUSTACEA. 



179 



which commences in the Lias, but attains its maximum in the 

 Middle Oolitic strata, being especially abundant in the fine- 

 grained Lithographic Slates of Solenhofen. In this singular 

 genus, the carapace is large and broad, and nearly quadrate in 

 figure, whilst the antennae are very small. Another singular 

 genus from the Solenhofen Slates is Megachirus, in which the 

 first pair of legs is enormously elongated, but not terminated 

 by chelae. In the Cretaceous Rocks are numerous Macrourans, 

 belonging to the genera Meyeria, Enoploclytia, Hoploparia, &c. 

 In many parts of the Tertiary series, especially in the London 

 Clay (Eocene), are numerous remains of Macrura, some of 



Fig. 122. Eryon arctifonnis, Middle Oolites [Solenhofen Slates). 



which have been referred, with more or less doubt, to such 

 living genera as Astacus and Palinurus. 



TRIBE II. ANOMURA. The Anomurous Decapods are dis- 

 tinguished by the condition of the abdomen, which is neither 

 so well developed as in the Macrura, nor so rudimentary as in 

 the Brachyura. The abdomen does not take any part in 

 locomotion, and does not terminate posteriorly in a caudal 

 fin. The penultimate segment of the abdomen, however, is 

 mostly furnished with more or less well-developed appendages. 



