THE VOYAGE OF H.M.S. CHALLENGER. 



imperfect. Their first undoubted appearance is in the Cretaceous rocks, where they are 

 represented by Homolopsis, Carter, from the English Gault and Greensand ; and an 

 allied form, Dromilites, Bell, occurs in the Eocene. Certain fossils are referable to the 

 Eaninidea, and even to the existing genus Ranina. 



DROMIDEA. 



Dromiacea, De Haan, Crust. Japon., p. 102, 1850. 



Dromidea, Dana, U.S. Explor. Exped., vol. xiii., Crust., part i. p. 400, 1852. 



Miers, Catal. New Zealand Crust., p. 57, 1876. 



Haswell, Catal. Austral. Crust., p. 138, 1882. 



Carapace subglobose or subquadrate, the frontal region narrow. Last pair of legs 

 and frequently also the penultimate pair subdorsal in position and of small size. 

 Abdomen folded under the thorax, the penultimate segment usually without appendages ; 

 five pairs of appendages in the female, the first pair rudimentary. Lateral thoracic 

 apodemata united in a common centre, forming a sternal canal. External maxillipedes 

 with the merus and ischium subquadrangular. 



To De Haan belongs the credit of having first characterised this group ; but the 

 family Dromiacea was referred by this author to his section Brachygnatha. It contains 

 the most highly organised Anomura, i.e., forms which have assumed for the most part 

 Brachyuran characteristics, so much so that Isy many competent authorities they are 

 placed in the Brachyura ; they are, however, separated fi'om the latter by the position 

 of the female openings and the rudimentary condition of the posterior legs. 



Family I. D r o m i d .E. 



Dromiens, !Milne-Ed wards, Hist. jSTat. des Crust, t. ii. p. 168, 1837. 

 Droinidx, Dana, U.S. Explor. Exped., vol. xiv.. Crust., part ii. p. 1428, 1852. 



Carapace subglobular, rarely flattened. Legs of moderate size, cylindrical, the fourth 

 and fifth pairs (fifth pair only in Dynomene) short and subdorsal in position, usually 

 prehensile. Eyes capable of retraction into well-defined orbits ; the antennules folded in 

 special fossse. Males of numj species (perhaps of all) with the vasa deferentia pro- 

 truded from the coxal joints of the fifth pair of legs and forming tubular prolongations. 

 Species inhabiting shallow water and moderate depths ; the majority protecting the 

 body by an Ascidian, Sponge, or valve of a Lamellibranch. 



Previous to 1858 the majority of the species were included in the genus Dromia of 

 Fabricius ; in that year Stimpson rearranged this heterogeneous collection into six genera 

 (five being new), relying chiefly for generic characters on the disposition of the sternal 



