;;7() MoLU'SKs ok 'iin-, (;al,\1'A(;()s — .stkai^ns. 



lii<li:iM s(:is and rlscw licrc, soiiict iincs ol' s«'\ t'r;il lioiirs' (liii;iii(>n ;iim1 

 of U'liilic loicc, imisl, in llic ll;llll^^^ ol' lliiiij^s, iiiclndc in ihv niiitc 

 rial nplilU'*! and swcpl bcloic I licni, aniinaU^ as well as inaninialc ob- 

 jccls. N() pari ()!■ Mir oarlli's snirarc, |H(>bal)I.v, is free Cnnn tlic oc- 

 casional \isilalinn of these violent, storms, Miouj;li tlicii- occnrrciicc. is 

 ininli more lVe(|nenl in som(> regions than others. '' N'olcanic (bisl," irom 

 tlie enii>l ion of a \ oleano on the island of St . \' ineent, West Iiidi(\s, fell 

 on an islan<l !•."> miles lo the windward in snch <|nantitics that, trt'cs 

 wi-rc ( rnshed to I he earth by the \\(>ii;ht of the mass.''* The i'jAfjfS of 

 most snails are not hea\ ier than i»arlicies of \olcanic dnsi oi' <lesert 

 Kiinds Ol, periiaps, the polh'n of tin* i)ine, and ina,\- be. moved separately 

 or as allaehed, <'ither to aerial drift oi' lln^ cnirent drift of the sea. 



'IMie more "icncral rci^ion w liieli inelndes witliin its area the (ilahl- 

 pa^'os is said to b(> free from sever«> storms; it is highly probabN', how- 

 »>\ ei', that in the c(mrse of years stoiins of urea t sevt-rily do occur, 

 and it is (piitt> nnliUely that any poi t ion of the earth's snrfae*^ is abso 

 Intcly exempt from occasional \isilations of this character. W ith the 

 hi^li \('locity that not infrecpn-id ly marks scNcre meteoric distnrbanc«'s, 

 a stoiniof \('ry short dnrat ion wtmid be snilicient to carry lit«'rall.\ on 

 "the win^s of the wind" plant seeds as well as tln^ minute e^j;s of 

 animals (»r the lar\a' of ins(>cts o\er distaui-cs no ureater than that 

 Ix'twecn the ( 5alaita.i;»is and the mainland. I 



1 ha\e quoted, in IIm> main literally, from IJaur, Af^assi/,, Kinney, etc., 

 in order to present to tin' I'cader, more particularly the student inter- 

 i'sted in the study of the Mtdlusca, the nioic im|»ortant physical fea- 

 tures exhiitited in this intcr«'stin,i; j;roup of islan«ls, their .yeo^iraphical 

 isolation vemote from the mainland of the Anu'rican continents, their 

 still greater distance IVom any (d" the Polynesian ishuuls, as well as 

 the moic local physical I'haracteiist ics, and tlu' ditVercuceobservable 

 anM)n|i; the various islaiuls when broujuht int(» comparison one with au- 



Clnss PELECYP013A. 

 Family OSTIMOID.K. 



(irmis OSTREA hiiiiu-. 



1. Ostiea folium (iiinl, 



Two vahcs; dill'ercnt individuals. 

 James Island. 



" \h. SliiMp, in I'lof. Acad. Niil. Sci. IMiilii.. ISiM). 



t 'I'lic I'lMiiiiolu f^Toiip, su|i|i(is(m1 to 1)»> ciUirrly <>iilsi«l(> i>(" llu< <'_vcl(>iu> licit, \\liii'h 

 inclii(li>s llu^ S;im(t:m .iiitl I'iji jnr(>ii|>N. \v:is Nwcpt by a I'hm'cc cydoiK^ in 1S78; and liu^ 

 Name Nioiin »<\lciidcil \o (in< S(icict.\ Islands. The oldest iiativi-s had not (>v«mi u tra- 

 dition of sni'li a storm occni'rin<r li(>loi'c in llu> rannn)tiis. 



\Vhil«< n-adin^ llic prool's of this paper tlu> tlaifv ])apers iia\ c < onlaincMl notices 

 of a disastMMis luMricinn^ on Hie « (last (d" Chile, l>_v which Hie mole nt oih< of (ln< 

 nitrate jiorls was cariii-d awav and dama;;e at this ]>oiiit was dont> to the 4'xttMit of 

 $1.")(»,(HH1. 



