894 0RTHANN — DISTRIBUTION OF DECAPODS [April 3, 



wish that my opinions may be investigated by other authors and 

 compared with material furnished by other groups of animals, as 

 well as with more complete and reliable geological observations to 

 be made in future. The way in which such investigations should 

 be carried on has been indicated in this paper. 



Finally, I want to point out that most of the ancient continental 

 connections here discussed are not treated for the first time, but 

 have been hinted at or more or less closely investigated by previous 

 authors, zoogeographers as well as geologists. But, unfortunately, 

 the former have not generally paid much attention to the results 

 obtained by the latter, and vice versa. Just this lack of a broader 

 view, chiefly among zoogeographers, has induced me to attempt to 

 harmonize both sets of facts, and the results here presented are pos- 

 sibly apt to serve as an apology for having undertaken this task 

 although much preliminary work remains to be done. 



APPENDIX. 



Relation of the Marine Decapod Faunas of the Eastern 

 and Western Sides of Tropical America. 



We have mentioned above (p. 359, footnote) that the facts fur- 

 nished by the characters of the marine faunas of either side of Cen- 

 tral America are frequently misunderstood or misrepresented. In 

 order to get at a proper understanding of the relations of the 

 Atlantic and Pacific Oceans, as revealed by these facts, I shall 

 endeavor here to give a (incomplete) list of identical, resp. closely 

 allied forms of Decapod Crustaceans, which are especially apt to 

 throw a light on this question. 



I have made it a point to include in this list only such forms as 

 give plain and unmistakable indications in this respect, that is I 

 have used only those cases in which the relations between the 

 Panamic and Caribbean region are the closest known, which, gen- 

 erally, is self-evident only when the respective forms (mostly 

 species of the same genus) are not known outside of American 

 waters. In genera or groups, where representatives are also 

 known from other parts (especially the Indo- Pacific region), it is 

 not always easy to determine the relation of the different forms, 

 and the question whether the West and East American forms are 

 the most closely allied ones remains unsettled : therefore I shall 

 disregard such instances. 



