84 THE NAUTILUS. 



ern shores of Middle and South America, with which this Report 

 deals. A comparison of the two faunas reveals many interesting 

 facts. The known fauna of the eastern Pacific deep sea contains 

 about 300 species of mollusks, belonging to 134 generic and subgen- 

 eric groups. The Antillean region possesses 174 groups and a much 

 larger number of species. "There are practically no species com- 

 mon to the two regions except at the southern extreme of South 

 America, where a few species extend northward on both shores of 

 the continent, but do not reach the Antillean or Panamic regions." 



The 300 species known from the Eastern Pacific deep sea fauna 

 belong to 67 families, but 159 of them belong to only 8 families, of 

 which the Turritidse or Pleurotomida (57species), Ledidtz (35 species), 

 Dentaliida and Pectinida are the most abundantly represented. The 

 Antillean deep water fauna has 174 generic and subgeneric groups, 

 against 144 in the Pacific, but of this number only 89 are common 

 to the two regions. Very many characteristic and prolific groups 

 in either fauna are unrepresented in the other. " These statistics 

 would indicate, if confirmed by further researches, that the separation 

 between the abyssal fauna of the Pacific and that of the Antilles is 

 very ancient indeed, for in the shallows many of these groups are 

 represented on both sides of the isthmus of Darien, yet have not yet 

 succeeded in reaching the deep water." The total absence of Tri~ 

 phorida, Cerithiopsidce* Marginellida and Pyramidellidce in deep water 

 on the Pacific side is especially remarkable. 



Some 254 new species of mollusca are described. A very useful 

 synopsis of the recent species and subspecies of Argonauta is given, 

 8 species being recognized. Much new and interesting material 

 for the systematic student is given, especially in the Terebrida, 

 Turritidce, Solemyacidce, etc., and as in all of Dr. Ball's papers, there 

 is a large store of information of value far beyond the limits of the 

 particular fauna under consideration. The changes in nomenclature 

 consequent on the resurrection of Bolten's Catalogue, are numerous, 

 and important to those engaged in similar work. Several lists are 

 appended, of interest to those engaged in faunistics : shells from the. 

 reefs and beaches of Easter Island and of Flint Island ; and a single 

 valve of a Pisidium, Corneocyclas magellanicus n. sp., was taken in 

 Magellan Straits, evidently washed in from some adjacent stream. 



As the pioneer work in a new fauna, this scholarly report will be 

 welcomed by conchologists the world over. 



