PLATE XXII. 



Fig. 



1. Pterichthys Milleri, crushed laterally; natural size. From Achanarras, 



Caithness, in the Collection of the Author. 



2. Distal portion or segment of the pectoral appendage in a specimen of 



Pterichthys Milleri from Tynet Burn, in the British Museum (35981). 

 Natural size. 



3. Pterichthys productus, showing the ventral plates of carapace seen from the 



internal surface ; natural size. From Lethen, in the British Museum 

 Collection (50111). 



4. Distal portion of the pectoral appendage in a specimen of Pteiichthys productus 



from Lethen, in the British Museum (39174). Natural size. 



5. Microbrachius Dicki, dorsal surface, seen from the internal aspect ; natural 



size. From Deerness, Orkney, in the Collection of the Author. 



0. Another specimen from the same locality ; natural size ; in the Collection of 

 the Author. 



7. Microbrachius Dicki ; anterior median dorsal plate, showing its articulation 



with the anterior dorso-laterals ; one third larger than natural size. From 

 John O'Groats, Caithness, in the Royal Scottish Museum, Edinburgh. 



8. Ventral aspect of the carapace of the same species from the same locality, 



magnified by one half. In the Royal Scottish Museum, Edinburgh. 



