SUBCLASS II 



EUCRUSTACEA— EUCARIDA 



761 



affinities with the Reptantia. The extinct genus Aegcr (Fig. 1475), which has 

 representatives in the Trias and also in the Solenhofen Lithographic Stone, agrees 

 with the Recent genera in having the third pair of legs chelate and much larger 

 than the first. It is, in all probability, a primitive member of this tribe. 



Representatives of the Caridea are not known with certainty earlier than the 

 Kimmeridgian, though some Carboniferous fossils have been described as having the 

 enlarged side-j)lates of the second abdominal somite, whicli are characteristic of this 

 tribe. In the Solenhofen Stone numerous genera occur, some of which, such as TJdora 

 Miinster, and Udorella Oppe], have exopodites on the thoracic legs, a primitive 

 character suggesting affinity with the Recent family Acanthephyridae. Other 

 Solenhofen genera, in which these exopodites appear to be wanting, are Blaculla, 



Fig. 1475. 

 Aeger tipularius (Schloth.). Upper Jura (Lithographic Stone) ; Eiehstadt, Bavaria. 2/.,. 



Hefriga and Elder Miinster. The Recent deep-sea genus Oplophorus i\Iilne Edwards 

 (Acanthejihyridae) has been identified, with considerable probability, in the Upper 

 Cretaceous of Westphalia. Some Caridea are found in frosh-water Tertiary deposits, 

 as for example Homely s von Meyer, from the Miocene of Oeningen ; but it is 

 impossible to say what relation they bear to the groups of Recent Caridea that have a 

 fresh -water habitat. 



Suborder B. REPTANTIA Boas. 



Body often depressed, rostrum often absent, small and depressed if present. First 



somite of abdomen distinctly smaller than the others. Leys stout, without exopodites, 



the first jMir usually much larger than the others. First five pairs of abdominal 

 appendccges commonly small, not used for swimming. 



§ 1. Palinura. 



This section consists of lobster-like forms w4th the rostrum very small or often 

 absent, with the carapace fused at the sides with the epistome, and the exopodite of 

 the uropods not divided by a distinct suture. It includes two tribes (1) the Eryonidea 

 and (2) the Scyllaridea (or Loricata). 



The Eryonidea comprise, among living forms, only a small number of genera 

 such as Polycheles Heller, and JFillemoesia Grote, which have chelae on the first four or 



