148 



Dr. W. T. Caiman on the 



in the Decapoda all are coalesced with the carapace. If this 

 were so it would constitute a strong, though not conclusive, 

 argument in favour of retaining the Euphausiidse in asso- 

 ciation with the other families of Schizopoda. As a matter 

 of fact, however, this difference between the Euphausiidse 

 and Decapoda does not exist. 



Junction of thoracic and abdominal regions of the hody, from the dorsal 

 side. A. Nyctiphanes norveyica (Euphausiacea) ; B. Pandctlus Bon- 

 nieri (Caridea). 



a, carapace ; b, intermediate plate ; c, tergum of first abdominal somite ; 

 d, tergum of second abdominal somite ; e, articular surface defined 

 by a groove on surface of second somite. The thorax and abdomen 

 are drawn slightly apart, to show the area occupied by soft articular 

 membrane between (indicated by shading). 



If the junction of thorax and abdomen in a typical 

 Euphausid such as Nyctijjhanes be compared with the same 

 region in one of the lower Decapoda (Penaeidea or Caridea), a 

 precise similarity of structure is found (see figure) . The poste- 

 rior margin of the carapace is concave on the dorsal side, 

 leaving between it and the apparent anterior margin of the first 

 abdominal somite an area of roughly lenticular outline, which 

 is fully exposed when the abdomen is flexed, and is occupied by 

 a firmly chitinized plate {h). Anteriorly this plate is overlapped 

 by the carapace, with which it is connected by soft articular 



