The fresh-water Crustacean fauna of Peru is represented by 

 one species of prawn which is also one of the oldest described 

 Chilean Crustacea, the "mason crab," Cancer cementarius, de- 

 scribed in the Abbe Don Molina's "Natural History of Chile." 

 (1776, anonymously, 1782 signed). 



The annotated discussion of the species is presented with 

 reference to their systematic classification. Geographical and 

 bathymetrical distribution of the species is also given. The greater 

 portion of the "Ara" and "Alva" Invertebrates herein discussed 

 are very rare specimens, not at all, or very sparsely represented 

 in any American museum, being hitherto known only from the 

 types or a few specimens variously fifty to a hundred years 

 old or even older, scattered in the museums of Asia, Australia, 

 Oceania, Europe, Africa, South and North America. In addition 

 to these rarities, numerous new species in several groups of In- 

 vertebrates were taken by the "Ara" and "Alva" and are depos- 

 ited in the type series of the Vanderbilt Marine Museum. Concise 

 discussion of the more significant rarities is given in the synopses 

 of the respective systematic divisions of Invertebrates reported. 



