HISTORY OF SESSILE-EYED CRUSTACEA. 



493 



vian genera are Arionellus, Carausia, Erinnys. Olenus and Microdiscus 

 characterise the Lirigula Flags, Dikelocephaliis ranges from the Lingula 



Fig. no. Agnostus. 



Fig. 109 Asaphus. 



Pig. in. Prestwicliia. 



Flags to the Tremadoc. The Harlech grits yield Plutonia, Pdlceopyye, 

 and Agnostus, which latter ranges to the Llandeilo rocks. 



Xiphosura. The King Crals 

 commence with Neolimulus in 

 the Ludlow rocks ; Prestwicliia 

 (fig. in) and Bellinurus are 

 found in the Coal-measures ; but 

 the group is absent from the 

 newer English strata, though Li- 

 multis is well represented in the 

 lithographic slate of Solenhofen. 



Merest omata. 1 The Mero- 

 stomata comprise an allied 

 group of Crustacea, in which 

 the abdominal segments re- 

 main separated as among trilo- 

 bites, but the appendages round 

 the inouth are developed after 

 the plan of the King Crabs. 

 Hemiaspis is found in the Wen- 

 lock and Ludlow, Slimonia in 

 the Ludlow rocks, Stylonunts 

 and Pterygotus in the Ludlow 

 and Old Ked Sandstone, while Eu- Restored by - Dr Henry woodward, F.R.S. 



ryptUTUS ranges from the Ludlow eyes ; 6. post-oral plate; c. antennulse ; d. mi- 

 , ,1 ri T -r T j_ tennse ; e. mandibles; f. maxillae ; q. swirn- 



to the Carboniferous limestone. ming f ee t ; 1-12 segmeuts, 13 teison 



The Phyllopods are mostly 



small Crustacea with a carapace often formed of two parts. They 

 are characteristic fossils of the Primary rocks. Hymenocaris is found 



13 



Fig. 112. Pterygotus. 

 by Dr. Henrj 



Henry Woodward : Palseontographical Society. 



