240 University of California Publications in Zoology | Vou. 14 
3, 4, and 5), and only 9.4 for the gravelly ones. The average for 
sand (group 3) is but 5.4, which is only about one-ninth that for 
pure mud. That such localities are relatively barren of molluscan 
life also appears from the consideration of the average number of 
species per station for group 38. This has been shown above to be 
considerably less than for the other types of bottoms. 
TABLE 7 
PREVALENT SPECIES FOR THE DIFFERENT TYPES OF BoTTOM 
i} Lo) 
2 =| to rc 
rs q OE 5 
= shies Salles 
BS tay St, os ees 
a a n wn Rn i) SG 
1 2 3 4 5 6 i 
(Obra helen, (Ce OIE), eee ae ee ose ee eee SEK EK, I ASC ie i 
Columbella gausapata ...........--..--0000. <0 x : 
, JHinnites giganteus) 22 Sys Paseo ae eX 
Malcom aye alli alee eee nee DES SCRE cok dle 2K NON ee 
IEC NDEAN SUA FUORI NEY EY aces ereeeanereeraeceei See x 5x > GMS eee 
Mia Com ayenia Bui ta)yes eee eee een OR SG ae 
Monia macroschisma ... xX 
Miopalliia se iientay sorseacesea seer earn eX 
Mop alliia mUS COS). -ceeseremeset tease ean 2 PG eee 
Miya Canlit ONC ay eee cee see enee eens Xi KK EEG comme 
Mya anenanian 280.35. 2s. pe Sa 
Meytiluscalitonni esse see ene eet, wie Heol Bet ie 
Mey tilusxe duis) 2-2 ee eee eee i OK BE Ks A 
IN S88 LOSS) ccc sec scteeccncesncsrece-cteesen eee wate) GEREN Wiescet Weed OC 
Nassa perpinguis XE ES 
INials Sa) Men Cay secce.cec- esc ose eee ee een ere = i ECE 
@stinea) Miri ay eng se esses o een eee Ki OG KRG 7 Ce 
DEAE (z yo) WG BEET, CO ENED Se eee ener tnern nese Sete x = 
arp bi a Shana LNG Bi sees sarceneeereteee cee neeeeaer x Ge ex 
Petricolay carditoud Gs) secs ce-s scent ees ececaaee ak, Wee eX 
holadide@arpemiitiay co fees cea anges Bow set die at 
Saxicava arctica ............. tee ee ne pee eee ee eS sh hn 
Saxidomus nuttalli -.... Gee Yerany -jeccs Meee eee 
Schizothaerus muttalli (2222 ees be RSC Oh ee 
SSD cq oveay tea eee cece eee aie) enbsl Se ge 
Spisullal (cabin Ov Sees eee nen rere ee Se oS ces 
Solem! i9LC@aruS occa ceeecae eee eee eee ee Case NC 
MelIimian at GONG e-cseerceee eee voce Mcae |e, Pee ae een ee 
Tellina salmonea x oS Ss 
Thais lamellosa Xo) OC ae 
Tor bonilla traneciscan ay eer os ee 
IKylObT Ya, SPs --p2c--c2nencececncnnnenennwernenecennennore) =nam se oe 
Vie iNcEN CPA OE, aoccnopctccacoomecceccecncaceoee cat See, OST S 
