A. E. Verrill — Decapod Crustacea of Bermuda. 455 



Probably the locality, Ascension I., given for Gecarciiais lateralis, 

 on p. 310, is erroneous, the species found there being G. lagostoma 

 M.-Edw. 



Aside from the widely distributed grai)soid crabs, found in all 

 tropical seas, very few of the Bermuda species are found on the 

 Pacific coasts of Central and North America. But many others are 

 represented there by closely allied species or subspecies.* The species 

 that have been considered identical or distinguishable only as varie- 

 ties by recent good authorities are as follows : 



Goniopsis cruentatiis * Percnon planissimton 



* Grapsus grapsus *jDomecla hispida 



"^ Geogrupsus lividns JEpialtusbituherculatus (varieties) 



*Pachygrapsxis transversus * Calappa gcdliis (varieties) 



* Planes mhiutiis Cycloes Bairdil (varieties) 

 * Plagusia depressa *Petrolisthes armatas 



Those preceded by an asterisk are circumtropical. 



It is well known that a considerable number of species of MoUusca, 

 Echinoderms, Anthozoa, etc., as well as Crustacea, are common to 

 West Africa, Brazil, and the West Indies. Such species may have 

 orio'inated on the African coast and from thence miajrated across the 

 Atlantic to South America, and thence northward to the W. Indies. 

 Florida, and Bermuda, during recent geological times. All the 

 species of Decapod Crustacea having this wide range exist for a 

 considerable length of time as free-swimming larval forms, in the 

 zoea and megalops stages. These larval forms may be carried long 

 distances by the prevailing oceanic currents, especially in the regions 

 of the trade winds. 



It is scarcely admissible to suppose that they could have traveled 

 in the opposite directions, against the currents, unless by human 

 agency, in recent times. 



Many Crustacea, including the higher and more active forms, 

 especially the grapsoid and cancroid crabs, are in the habit of hiding 

 among the clusters of bai'nacles, etc., attached to the bottoms of 

 vessels, and in this way they may be carried across the oceans in any 

 direction, so long as the temperature of the water is suitable for 

 their existence. In this way many tropical species reach the New^ 

 England coast in summer, but die out during the winter. 



* Mr. Walter Faxon has given, in parallel columns, comparative lists of the 

 closely related species occurring on the two coasts. See Mem. Mns. Comp. 

 Zoology, vol. xviii, pp. 235-337, 1895. 



