BEITISH ASSOCIATION. 265 



truncate, separated by a short transverse suture from a small, narrow, 

 somewhat quadrilateral plate, which bears the internal antennae, and is 

 probably the remains of the second or internal antennary ring, the frontal 

 plate itself representing the external antennary or third ring of the 

 typical crustacean; beneath this is a broad, well-marked plate, the 

 epistome. 



Philoscia. Plate XX., Pigs. 1 to 6. 



The inferior border of the frontal ring is nearly straight across, the 

 transverse suture well marked, nearly on a level with the superior mar- 

 gin of the external antennae, its superior margin curved, raised, and 

 passing slightly beyond the frontal line of the cephalic segment, shutting 

 out the orbit from the insertion of the external antennae, and a deep sul- 

 cus separating it from the external angle of the orbit, the third ring 

 being thus transverse and narrow. The second ring is nearly as deep as 

 the third, and well marked ; the epistomal plate narrow, and formed of 

 two triangles placed apex to apex. The orbits are open below and be- 

 hind. 



PMlougria. Plate XXI., Pigs. 1 to 4. 



Nearly a similary arrangement prevails, but the lateral ridges around 

 the insertion of the external antennae are somewhat more strongly 

 marked. 



Oniscus. Plate XXL, Pigs. 5 to 7. 



The external angles of the superior margin of the third ring are pro- 

 duced into a broad lobe, which covers over the origin of the external 

 antennae, it is then continued across, projecting slightly over the frontal 

 line of the cephalic segment ; the transverse suture is well marked. 

 The second ring very narrow, almost obsolete. The lateral lobes are con- 

 tinued backwards, and are separated by a suture from the external in- 

 ferior border of the cephalic segment, which completes the orbits. 



Porcellio. Plate XIX., Pigs. 1 to 10. 

 External angles of third antennary segment still more developed, 

 the superior margin raised into a lobe which projects above the frontal 

 line of the cephalic segment, and gives the head a trilobed appearance. 

 This lobe, though sometimes badly marked, Porcellio pruinosus (Br.) f 

 P. frontalis (Zereb., notPJdw.), for example, is present in all the species 

 I have had an opportunity of examining. 



Armadillium. Plate XXL, Pig. 3. 

 The eyes are supported on the cephalic segment alone, the margin 

 of this is raised, forming an angular projection in the middle of the 

 forehead, passing back from whence, as before stated, it forms the orbital 

 margin, to the entire exclusion of the third segment, the lateral lobes 

 here being remarkably small, and derived entirely from the cephalic 



