BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Solenosteira Pallium 
Truncaria Acesta 
Tritonoharpa Archivesica 
Capulus Pholadidea 
Clanculus Dermatomya 
Zeidora Hemithyris 
Spinula Terebratella 
Malletia (s. 8.) Magellania 
Neilo Basiliola ? 
Even in the groups common to both regions there are some interesting 
' differences. 
Mangilia is numerous in the Atlantic, rather sparse in the Pacific ; 
Fusinus rare in the Pacific, numerous inthe Atlantic. Anachis, Murex, 
Scala, Calliostoma, Dentalium, Cadulus, Propreamusium, Phacoides, and 
_Venericardia are relatively common on the east and sparse on the west 
of the continent. The total absence of the Triphoridae, Cerithiopsidae, 
and all the group of Marginellidae from the fauna of the west is aston- 
ishing, and incomprehensible with our present knowledge. Why should 
Vesicomya on the east be moderate or small in size, and on the west 
large even to gigantic ? 
Why are there no Pyramidellidae of any sort in deep water on the 
Pacific side? Why should European or Japanese types of Pecten, Lima, 
etc., appear on the west coast and be absent from the Antilles? These! 
questions will doubtless be answered in the future, but with our present 
knowledge we can make no satisfactory reply. 
After a general survey and comparison of the two faunas, Atlantic and 
Pacific, as developed by the “ Albatross” and other dredgings, it may be 
concluded that the deep-sea fauna of the eastern Pacific is composed of 
several elements. We have first a comparatively limited number of 
abyssal forms of wide distribution. These are doubtless the descendants 
of very ancient migrants to the deeps, and their precise number and 
character can only be definitely known after much more extended ex- 
ploration of the floor of the deep sea. Still, from our present knowledge, 
it is practically certain that there is such a group of species, although 
we cannot as yet state how many of them there are. 
Secondly, there is a considerable number of species characteristic of 
the Antarctic and Magellanic regions. Whether they are descended from 
the present shoal-water fauna to which they are systematically akin, 
members of which may have strayed into deeper water from time to 
time and become acclimated there, or whether the deep-sea fauna and 
the littoral fauna are both descendants of an Antarctic fauna which 
