1895.] NATURAL SCIENCES OF PHILADELPHIA. 173 



A STUDY OF THE SYSTEMATIC AND GEOGRAPHIC DISTRIBUTION OF 

 THE DECAPOD FAMILY CRANGONIDJE BATE. 



BY ARNOLD E. CtftTMANN. 



In a former paper 1 I gave in general terms the limits of the Indo- 

 Pacific literal region, to which I added a study of the origin of the 

 recent literal regions of the world. As these considerations, founded 

 upon the geographical distribution of the Decapoda, contain but a 

 few detailed investigations, it is necessary to go more into detail when 

 a separate group of Decapoda is examined and to state the relations 

 to the principles given in the paper quoted. In 1891 I revised the 

 genera Palaemon and Bithyms 2 and gave an account of their 

 geographical distribution. In 1894 I published an account of the 

 family Atyidre! 3 These groups of fresh water Crustacea are wholly 

 unlike each other in respect to their geographical range and agree 

 only in that they are true tropical animals. Whilst the Palcemon 

 and Bithynis group of the Palsemonida; is a very recent one, related 

 in its distribution, without doubt, to the limits of the recent marine 

 literal regions, the family Atyida? is comparatively an ancient one, 

 showing in no way relations to the former. 



In the present paper I will treat of a true marine group, the 

 family of Crangonidse, which is characterized by the adaptation of 

 most of its members to the cold waters of the Arctic and deep sea 

 regions. 



Fossil remains of Crangonid?e are unknown. In all species referred 

 with more or less doubt to this family, the typical characters are not 

 evident. The absence of Crangonidoe from the Tertiary deposits 

 agrees with their morphological characters and their supposed recent 

 development. They form the most extreme end of one of the two 

 main branches of the Eucyphidea. 4 The principal character is the 

 more or less reduced condition of the second pair of pereiopoda. The 



1 Jenaische Denkschrift. VIII, 1894, p. 68 P. Crustaceen in Seinon, Zoolog. 

 Forschungsreisen in Australien und dem malayischeu Archipel. 



2 Zoologische Jahrbiicher, V, 1891, p. 693-750. 



3 Proceed. Acad. Nat. Sci. Philadelphia, 1894, p. 397-416. 



4 Ortmann, Zoolog. Jahrb., V, 1890, pp. 462, 463. 



