Rock numbers* 
Dimensions in inches 
Weight in pounds —......... 
Entodesma saxicola 
Zirfaea gabbi .... 
224 University of California Publications in Zoology — [Vou. 14 
at the surface, while nine of them show considerable percentages of 
lime at depths from 40 to 140 centimeters. In the other divisions of 
the bay the tubular samples are, with a very few exceptions, nearly 
uniform in respect to the lime content from the top to the bottom. 
In the lower extremity of the bay five of the ten sections show shells 
only in the middle portion of the sample, indicating a change from an 
unfavorable to a favorable and then back again to a comparatively un- 
favorable environment for the mollusks. At two of the five remaining 
stations the sampling apparatus did not penetrate to the shell horizon, 
which appears to be quite extensive in that region. 
The reason for such fluctuating conditions is not evident. Were 
it not for the bottom stratum of relatively limeless mud the present 
unfavorable conditions might be attributed to some factor introduced 
as a result of the proximity of the cities of San Francisco, Oakland, 
and Alameda. These changes may be due to the variations in the 
silting up of the basin of deposition, whereby during certain periods 
deposition proceeded at too rapid a rate to favor abundant mollusean 
life. Such variations in sedimentation might be expected as a result 
of local diastrophic movements, such as are indicated by changes of 
level registered by the Indian shell mounds around the bay. Or pos- 
TABLE 4 
FAUNA OBTAINED IN CAVITIES IN Rocks at Stations D 5845 anp D 5846 
Species 
Crepidula nivea 
rene ertat 1 2 3 4 5 6 i 8 aka) aie aks} ae Gy als) 
= 
s 
is) 
wa ae a5 ~~ ia 
> ive) No} x © % a V-) & inl 
. a x SCS ayy. Ne) K <n x < x eS 
cial ne x oa) = x © 2 © er eS eS mn Oo 
Se eS Bo gee. Ok ee ee 
s ea x x a as oa, I a ef LAGS = oo 
fe) ited aa ~ Sa ol a io cl I (o>) Oo vA x tal 
14% 2 20 2 6% 2%16% 6 6 8% 19 8 5 14% 19%6 
Zest x E 
ee eee Wy Westen oe eae aso. Ge, cates eee ee eee mm 
Kellia lapuerosi -........ -... See) RS ete cere teks ET Gee Se ee CS 
Hinnites giganteus ...... .... .... ro igteet psdkj 528 Se. Sector Sl ee x 
Macoma inquinata .... -... siz hewese * sik) “Ghee, Sie SEV eee eee ee Eee he ee = 
Paphia staminea ......... .... Sas) assy (ests. rsben © kde Peet EEL OX : E C 
Pholas pacifieus ......... .... ses | Seas) WX we SE) eee a ee 
Pholadideasovordea: sxc. Wave eect, ears ee eee ot 
Pholadidea penita ...... -... Kinet EX : x ox 
Petricolaycanditoides ss, $9 Gee cs | core ste eee eee CCX CQ 
Ostrea lurida; = SAR Ae Oem eI Nae Meee eae Neth We Ie = 
Saxicava arctica ......... .... sate, Qekh Dtabee.. Bx ote 
x = 
* Rocks 1-6 inclusive, came from station D 5845, the others from D 5846. 
7 Living specimens. 
na 
cS 
a 
a 
13 xX Th X 6% 
