1899.] A. Alcock — Carcinnlogical Fauna of India. 127 



In comparing the above synopses of characters it will be seen that the Dromidea 

 as a whole have developed along Brachyurons lines in respect of the antennal 

 flagella, orbits, external maxillipeds, and shape of the carapace, but have kept near 

 to the primitive (Homarid) branchial .arrangements. Whereas the Homolidea as a 

 whole show a tendency to approach the higher Brachyura in the reduction of the 

 branchiaa, but have not departed much from the primitive (Homarid) type in the 

 form of the antennal flagella, external maxillipeds and very imperfect orbits. 



Tribe I. DROMIIDEA. 



The Broviiidea which, notwithstanding the more Brachjurous form 

 of the carapace of their best known representatives, are as a whole more 

 primitive than the Homolidea may be divided into three families — 

 Homolodromidse, Dynomenidse and Dromidae — characterized as follows : — • 



Family I. Homolodromidj). 



Carapace longer than broad, convex in both directions, tlie true 

 cervical and the branchial grooves botli present. 



Front cut into two prominent teeth, between which, but on a much 

 lower plane, a third small tooth is sometimes present. 



Antennal flagella longer than the carapace. 



External maxillipeds with a marked pediform cast. 



Chelipeds equal, slender, though stouter than the legs. 



First two pair of legs much longer than the chelipeds : last two 

 pair much shorter than the first two pair, subdorsal, prehensile. 



The abdomen in both sexes consists of 7 separate segments : there 

 are no lateral platelets intercalated between the 6th and 7th segments. 



The gills are trichobranchiae, or are intermediate between tricho- 

 branchiae and phyllobranchise : the gill-plumes are very numerous — 

 there may be as many as 20 on either side. 



Epipodites are present on the chelipeds and first two or three pairs 

 of legs. 



The sternal grooves of the female are short, ending at the level of 

 the genital openings. 



To this family belong the following genera : — 



1. Homolodromia, A. Milne Edwards, Bull. Mus. Comp. Zool., VIII. 1880, 

 p. 33 : Recneil de Fig. de Crustaces Nouveanx, pi. 39, fig. 2. 



2. Dicranodromia, A. Milne Edwards, Ball. Mus. Comp. Zool., VIII. 1880, 

 p. 31 : Recueil de Fig. de Crust. Nouv. pi. 10. 



3. *Arachnodromia, Alcock, seq. 



Family II. DynomenidvE, Ortmann. 

 Bynomenidx, Ortmann in Bronn's Thier Reich, V. ii., Arthropoda, p. 1155. 

 Carapace variable, either longer than broad and convex, or broader 



