18 



The chelipeds are equal and are rather slender, though considerably stouter 

 than the legs : the fingers are well calcified and are hollowed en cuiUere, the 

 tip of the dactylus shuts into a notch in the tip of the opposed finger. 



The legs are cylindrical : the first two pairs are very long, the last two are 

 short, subdorsal in position, and cheliform rather than subcheliform. 



The sternal grooves of the female end opposite the openings of the oviducts, 

 without tubercles. 



The abdomen of both sexes consists of seven distinct segments. In both 

 sexes the pleurae of the 3rd-6th abdominal somites are remarkably free and 

 independent {i. e. not in contact with those in front and behind) and the last 

 abdominal tergum is nearly as long as the preceding five combined. In the male 

 this last tergum is marked in a most suggestive way (see figure). 



The Branchial Formula of Aeachnodeomia. 



Somites and 

 their appendages. 



VII. 



VIII. 



IX. 



X. 



XI. 



XII. 



XIII. 



XIV. 



5 + 6 ep. II 4 20 + 6 ep. 



The formula is thus the same as that given by Bouvier for Homolodromia. 



This crustacean so closely resembles the Homolodromia described and figured 

 by Milne Edwards* and referred to by Bouvier,! that at first sight it might be 

 supposed to be the same form. 



In Homolodromia, however, it is distinctly stated that the antennules are 

 not retractile, and that there are no special orbits. 



In Arachnodromia, on the other hand, there are orbits formed on exactly the 

 same plan as, and hardly less perfect than, those of Dromia, and they afford 

 complete protection to the retracted eyes and antennules, the antennulary flagella 

 folding, as in Dromia, behind the eyes. 



• A. Milne Edwarda, Bull. Mus. Comp. Zool. Vol. VIII. 1880, p. 32, and Recueil de fignrea de Crustaces 

 Nonveanx etc. pi. 39, fig. 2. Not the Homalodromia of Jliera. 



t E. L. Bonvier, Bull, Soc. Philom. Paris (8) VIII. 1895-96, p. 37, etaeq. 



