﻿PLATE XV. 



UPPER SILURIAN CRUSTACEA. 



Order — Merostomata. 



Sab- Order — Eurypterida. 



Pterygotus bilobus, var. y,perornatus. 



Fig. 



1. Head and four anterior segments of body of Pt. bilobus, var. y, showing the larval 



eyes (le), the compound eyes (o, o), and the right swimming-foot (ectognath), still 

 attached in situ. 



2. The greater part of the body of another specimen, having portions of the thoracic and 



the entire series of abdominal somites preserved. 



3. A very beautifully preserved detached lip-plate of Pt. bilobus, var. y, showing the 



truncated posterior border (a), by which it was attached to the head. The surface 

 is beautifully squamate. 



From the Uppermost Silurian of Lesmahago, Lanarkshire. 



Drawn, of the natural size, from specimens preserved in the British Museum. 



