208 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
but do not reach the Antillean or Panamic regions. A few species like 
Bathyarca corpulenta, or some of the Solemyas, have a very wide range 
over the floor of the Pacific Ocean. Among brachiopods Discinisca 
atlantica is common to the two oceans, and in the Atlantic to both, — 
hemispheres. The presence of the Terebratulina crossec in both Japan 
and Patagonia, to my mind, requires confirmation. I have seen nu- 
merous specimens from Japan, but nothing of the kind from the Magel- 
lanic region, and this is not an abyssal species, like Terebratula 
moseleyi. 
That a certain proportion of the North Pacific fauna of the deep sea 
originated in the south seems highly probable. The north, however, 
seems also to have contributed its migrants. When the question of 
“bipolarity ” is raised, and based upon a few supposedly identical 
species, it is but feebly, if at all, supported. But if generic and sub- 
generic groups be taken instead of species for comparison, an undeniable 
‘“‘bipolarity ” is displayed. But this question is one with which our 
present faunal area is only distantly connected. 
Our fauna, which I shall for brevity in this discussion call the ‘“ Pa- 
cific” fauna, contains about 300 species, belonging to sixty-seven families. 
Of these eight families furnish more than half, and three of these family 
groups contain one-third of the whole fauna. 
Murritidaeicontains <0 Mele si) ane cis ee al it etaaOUMs DECIes 
Ledidae OG Acne inches a mies Real PacMan Gosdinntel ls tenancy 
Dentaliidae ‘“ Ne MeIRRTE aes i aoek Soho aeen aca wee ANE aCe 
Pectinidae ee PRES les A OU Rye male MRE ren Do] at 1 
Nuculidae and Naticidae,each ........id211 «* 
Mrochidae:and Limopsidave;each’ 24 a) (yawns nO) 
The total number of species in these eight families is 159, leaving 141 
species for the other fifty-nine families, or little more than two species 
apiece. 
The Antillean fauna has 174 distinct generic and subgeneric or sec- 
tional groups of importance represented. The Pacific fauna has only 
144. But of all these groups only eighty-nine of mollusks are common 
to both faunas and six of brachiopods. 
The Pacific has three groups of brachiopods and twenty-seven of mol- 
lusks not represented in the Antillean fauna. 
The Antillean has three groups of brachiopods and seventy-six of mol- 
lusks not represented on the Pacific side. 
These statistics would indicate, if confirmed by further researches, 
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