4 Addison E. Vcrrlll, 



Station and public Aquarium, there are excellent opportunities to 

 carry on such researches. 



In the important memoir of Brooks and Herrick, on the meta- 

 morphoses of the Macrura (Mem. Nat. Acad. Sci., vol. v, 1891) 

 the metamorphoses and structures of a few Bermuda species are 

 given; viz., Stenopus hispidus; Alpheus heterochalis ; A. packardi 

 (erroneously identified as A. minus}, and Synalpheus brevicarpus. 

 They found remarkable variations in the larval forms, supposed 

 by them to be of the same specie^ of Alpheus and Synalpheus. 

 The most notable cases of this kind were due to erroneous identifi- 

 cations of the species of those difficult genera, as shown by 

 Coutiere. Many more studies of that kind should be made on the 

 numerous closely related species of that group. 



On account of the existing confusion in the literature, and the 

 inherent difficulties in determining the numerous species of Alpheus 

 and Synalpheus, I have treated those genera in greater detail than 

 most others, describing and figuring, with many structural details, 

 all the species known to me from Bermuda, as well as some closely 

 allied species from other American localities, hoping that students 

 of their embryology will be enabled by this means to correctly name 

 the species they may investigate hereafter. In other groups gen- 

 eral figures, at least, are given of nearly all the species, and in most 

 cases the structures of some of the appendages are also figured. 



Hitherto some of these species have not been figured at all ; 

 others have been figured only in foreign works, many of them 

 very imperfectly. The photographs and drawings, unless otherwise 

 indicated, are by A. H. Verrill. 



Suborder MACRURA. Crawfishes, Lobsters, Shrimps, and Prawns. 



Key to the Tribes and part of the Families. 



A. Body not compressed. Rostrum depressed, sometimes wanting. First 

 abdominal segment shorter and narrower than the following. Abdom- 

 inal appendages (pleopods) not oar-shaped. The articulation between 

 the carpus and propodus of the chelipeds is at two fixed points. 

 Branchiae filamentous. 



Reptantia = Trichobranchiata = Astacina DeHaan. 



B. Abdomen or pleon large and strong with the segments overlapping. 



Carapace large and firm. 

 D. None of the legs have chelae, except the 5th pair in the adult 



female. No appendages on ist segment of pleon ; outer antennae 



