12. Differentials in Behavior of the Two Generations of _Salpa democratica_ Relative to the Temperature of the Sea, by Ellis L. Michael. Pp. 239-298, plates 9-11, 1 figure in text. March, 1918 .65 13. A Quantitative Analysis of the Molluscan Fauna of San Francisco Bay, by E. L. Packard. Pp. 299-336, plates 12-13, 6 figs, in text. April, 1918 .40 Transcriber's Notes Emphasis Notation: _text_ - italicized =text= - bold All of the text presented here is a copy of the original article's text with the following exceptions:< 1. Typographical Corrections A. Page 509 - Medicine Bow Mts., 10 200 => 10,200 B. Table 1. Added missing period in column 1 U. S N. M. no. => U. S. N. M. no. C. Vol. 17 number 16 => 15 of the "UNIVERSITY OF CALIFORNIA PUBLICATIONS" listing 2. Placement of UNIVERSITY OF CALIFORNIA PUBLICATIONS Listing The original publication had this list beginning inside the front cover and continuing on the back cover (inside and out). Here it was moved to the end of the book for readability. Inconsistancies in the formatting of the list (i.e., periods, commas, etc.) were left as presented in the original (with the exception noted above).