

[Reprinted from the Academy of Natural Sciences, March 13, 1895.] 



A STUDY OF THE SYSTEMATIC AND GEOGRAPHIC DISTRIBUTION OF 

 THE DECAPOD FAMILY CRANGONIDJE BATE. 



BY ARNOLD E. ORTMANN. 



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

 Paeific litoral region, to which I added a study of the origin of the 

 recent litoral 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 Palcemon and Bithynis 2 and gave an account of their 

 geographical distribution. In 1894 I published an account of the 

 family Atyida?. 3 These groups of fresh water crustácea are wholly 

 unlike each other in respect to their geographical rauge 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 

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

 showiug in no way relations to the former. 



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

 family of CrangonidaB, 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 Crangonidre are unknown. In all species referred 

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

 evident. The absence of Crangonidre from the Tertiary deposits 

 agrees with their morphological characters and their supposed recent 

 development. They form the most extreme ençl 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 Semon. Zoolog. 

 Forschungsreisen in Australien und dem malayischen Archipel. 



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



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

 i Ortniann. Zoolog. Jahrb.. Y, 1890, pp. 462, 463. 



1 



