MACROURA. 



497 



rounded prominence at apex, which is abruptly narrower than the 

 preceding part. Carapax concave behind, with posterior angles 

 rounded ; a rounded prominence on the margin posterior to eyes, just 

 anterior to base of first pair of feet. The fifth pair of legs is the shortest, 

 the second next shortest, The last joint is oblong (half as long as 

 preceding), and spinous beneath, with six or seven stout spines, of 

 which the second from apex is stoutest; also one spine near apex on 

 outer margin. There is a spine directed upward on the base of the 

 inner antennae, as it lies folded adjoining the beak. Whole body — 

 the carapax, abdomen, exterior maxillipeds, and legs — pubescent with 

 very short hairs. Exterior maxillipeds not in contact ; third joint 

 much smaller than second. 



The species may be the young of a Plagusia. 



Tribe III. MACROURA. 



Before considering the classification of the Macroura, we must 

 again bring into view the prominent characteristics distinguishing the 

 typical forms among them, from those of the Brachyura. These cha- 

 racteristics are not equally pronounced in all the Macroura. There 

 are variations of development or condition, and these variations mark 

 the greater or less affiliation of the species to the Brachyural, or Ma- 

 croural type. The same organs and the same range of characters, 

 therefore, which separate the grander divisions of Decapods or Eu- 

 branchiates, are generally of pre-eminent importance in tracing out 

 the minor groupings, and their value in the former case is to a 

 certain extent, a criterion of their value in the latter. We must, 

 therefore, have these characteristics in mind, as the first and most 

 essential step towards a correct appreciation of the natural distinc- 

 tions and arrangement of the species. The attention of the reader is 

 therefore again directed to these characteristics, as detailed on page 

 49 of this volume. 



There are also relations to the Anomobranchiates, or the Squill a 



125 



