BALCH : LIST OF MARINE MOLLUSCA. 
137 
\b cjo are “southern,” and 36 H- % unassignable. I think the 
similarity of the figures in gasteropods and pelecypods consid¬ 
ered separately shows that these percentages stand for a real fact 
of distribution. Two faunas overlap, the more southerly contribut¬ 
ing rather more than twice as many species as the northerly. 
The following species which do not occur at Coldspring Harbor 
(so far as known) are given by Perkins (’69) as occurring at New 
Haven on the opposite shore of Long Island Sound about forty 
miles to the eastward : Amy da dissimilis Stimps. (= Astyris 
zonalis Linsley), three specimens found among a lot of A. zonata / 
Scalaria multistriata Say (— Scala ni. Say), very rare; Odostomia 
dealbata Stimps., very rare; 0. impressa Stimps., not common; 
0. seminuda Gould (= 0. seminuda C. B. Adams), very rare; 
Pleurotoma brunnea Perkins (= JBela plicata Adams), one speci¬ 
men thrown up by the waves; iSimnia uniplicatida Adams ( = S. 
uniplicata Sowb.), one specimen probably brought up on southern 
oysters; Pissoa aculeus Stimps. (= P. aculeus Gould), common 
under stones and on algae near low water; Pissoella f eburnea 
Stimps. {= Pissoa eburnea f Stimps.) one beachworn specimen 
taken by Dr. Perkins which Verrill (’73, p. 655) remarks “may 
have been some other species.... I have seen no undoubted shells 
of this species south of Cape Cod ”; Skenea planorbis F. & H. 
(—S. planorbis Fabr.), taken with Alexia myosotis , not com¬ 
mon; Lacuna vincta Gould (= L. vincta Turton), not very com¬ 
mon ; Littorina irrorata DeKay (= X. irrorata Say), not at all 
common ; Tornatella puncto-striata C. B. Adams (= Actaeon p. 
C. B. Adams), dead on the beach, not common; Cylichna oryza 
Stimps. (— Cylichnella o. Totten), dead on the beach, very rare ; 
Cyrtopleura truncata Tryon (z — Pkolas (Lamed) t. Say), clay and 
peat at high water, not rare ; Martesia cimeiformis Tryon (= M. 
cuneiformis Say), one specimen in a pile of beach shells ; Saxicava 
arctica Linn., sand near low water, not common ; Corbula contracta\ 
Say, sand at low water, not common ; Siliqua costata Con. (— S. 
costata Say), very rare and small; Angulus polita ? Tryon (= 
Tellina p. Say), a few specimens doubtfully so referred ; Kellia 
planulata Stimps., in accumulations of small shells on shore, not 
common; Brachydontes hamatus Say (= Mytilus h. Say), abun¬ 
dant on southern oysters, doubtful if it is naturalized. 
The following species occurring at Coldspring Harbor do not 
appear in Perkins’s list: Chaetopleura apiculata Say, abundant; 
