﻿PLATE VIII. 



DEVONIAN CRUSTACEA. 



Order — Merostomata, Dana. 



Sub- Order — Eurypterida. 



Fig. 



1 . Under side of Pterygotus anglicus, Agassiz, restored. 



2. Upper side of ditto. 



Fig. 2. /. Larval eje-spots {ocelli). 

 ,, 1. m. The rnetastoma or post-oral plate. 



„ I. op. The operculum (representing the coalesced pair of appendages be- 

 longing to the vii th somite). 

 „ 1. a. Anal aperture. 



Figs. 1, 2. l. The eyes. 



„ 2. The chelate antennae. 



„ 3. The mandibles (endognaths, Huxley). 



„ 4. First maxillae ( ditto „ ). 



„ 5. Second ditto ( ditto „ ). 



„ 6. Maxillipeds (ectognaths, „ ). 



*, i. Position of small somewhat triangular plate united to the border 

 of the penultimate joint, and overlapping the oval terminal 

 palette. (See page 35.) 



„ vii. The head-shield, bearing the ocelli {I) and large compound eyes 



(l, i), and the operculum, or thoracic plate, which covers the two 

 anterior thoracic somites (viii andix) upon their ventral surfaces. 



„ viii— xiv. Thoracic somites. 



„ xv— xix. Abdominal somites. 



xx. The ' telson ' or terminal segment. 



