CRUSTACEA. DECAPODA 329 



Section 1. Macrura 



This section includes the lobsters, shrimps, and cray- 

 fishes. The abdomen (fig. 143, c — e) is long, well deve- 

 loped, and ends in a large tail fin (e,f) formed by the 

 telson and the appendages of the sixth abdominal segment. 



JEger. Body laterally compressed. Abdomen long. Rostrum 

 long, with small tubercles. Antennules nearly as stout, but not so 

 long as the antennas. Last maxillipedes long, with chelae. Third 

 pair of ambulatory legs longer than the others ; the fourth and fifth 

 pairs slender and flattened, without chelae. Trias and Jurassic. 

 Ex. JE. tipularius, Solenhofen Limestone (Upper Jurassic). 



Eryon. Cephalothorax flattened, broader than long, with a 

 median dorsal ridge on the posterior part ; the lateral margins 

 usually dentate, and at the anterior third are deep notches. 

 Rostrum short. The first four pairs of ambulatory limbs on the 

 thorax bear chelae, the anterior pair being larger than the others. 

 Abdomen of about the same length as the cephalothorax ; the first 

 segment very short. Telson trigonal. Trias to Cretaceous. Ex. E. 

 antiquus, Lias ; E. propinquus, Solenhofen Limestone. 



Grlyphea (fig. 143). Cephalothorax ornamented with granules ; 

 rostrum short. In front of the cervical suture are several spiny or 

 tuberculate parallel ridges which extend towards the anterior 

 margin. Posterior to the cervical suture are generally two other 

 grooves. The anterior pair of ambulatory limbs are much longer 

 than the others ; all are without chelae. Abdomen long. Trias to 

 Cretaceous. Ex. G. regleyana, Oxfordian ; G. tenuis, Solenhofen 

 Limestone (Upper Jurassic). 



Meyeria. Cephalothorax laterally compressed, with a sharp 

 rostrum, and a deep V-shaped cervical suture ; with sharp, serrate, 

 longitudinal ridges on the dorsal surface ; the sides of the cephalo- 

 thorax covered with sharp granules. Abdomen semi-cylindrical, 

 longer than the cephalothorax, and ornamented with longitudinal 

 rows of granules. Lower Cretaceous. Ex. M. magna. 



