370 Prof. Allman on Chelura terebrans. 



Availing ourselves therefore of the characters derived from 

 these considerations, the families of the Amphipodous Crustacea 

 may be analytically arranged as follows : — 



Fourth and liflh abdominal segments confluent. Ab- 



Familij. 



dominal appendages of the fourth and fifth pair ^ Ciieluuidjj. 

 very different in form (heteromorphous). 



AbO 

 pair I- Cm 



Fourth and fifth abdominal seg- 

 ments distinct. Abdominal 

 appendages of the fourth and 

 fifth pair nearly similar in 

 form (isomorphous). 



Mouth concealed l 



by the maxil- 1-Gammarida;. 

 lary feet. J 



n-l 

 he lir 



St. J 



Moutli not con- 

 cealed by the^ HvPERiDiE. 

 maxillary feet. 



EXPLANATION OF PLATES XIII. and XIV. 



Plate XIII. 

 Fig. 1. Chelura terebrans magnified. 



Fig. 2. The head deprived of the antennae and viewed from above. 

 Fig. 2». One of the superior antennce. 

 Fig. 3. One of the mandibles. 



Fig. 4. A spine from the inner edge of the mandible.- 

 Fig. 5. Molar surface of the mandibular tubercle much magnified. 

 Fig. 6. Portion of the same still more highly magnified. 

 Fig- ^. One of ihejirst pair of maxilla;. 

 Fig. 8. One of the maxillce of the second pair. 

 Fig. 9. Upper lip viewed on its oral aspect. 

 Fig. 10. Lower lip viewed on its oral aspect. 

 Fig.l\. Maxillarg foot of the leftside. 



Plate XIV. 



Fig. 12. Terminal portion of one of the^r,s^ /?a?> of thoracic feet. 



Fig. 13. One of the pectinated bristles of its penultimate joint. 



Fig. 14. One of the second pair of thoracic feet. 



Fig. 14*. Thoracic foot of the seventh pair. 



Fig. 15. An abdominal foot from one of the first three pairs. 



Fig. 1 6. One of its plumose setcs. 



Fig. 17. Posterior portion of abdomen deprived of its first and second pairs 



of appendages and viewed from above. 

 Fig. 18. One of the first pair of appendages from the great abdominal trunk. 

 Fig. 19. First three abdominal rings. 



disproved, and the absence of distinct epimerae is but a slight degradation 

 from the condition presented to us in the gressorial Gammaridce. The L(b~ 

 modipoda are indeed a group in every way referable to tlie Ami)hipodous 

 type, and there is much reason to believe that they should never have been 

 separated as a distinct order. See Kroyer in the ' Isis ' for 1846, Heft ii. 



