1918 ] Packard: Molluscan Fauna from San Francisco Bay 231 
The reproductive periods of a comparatively few mollusks are 
known and none that belong to this fauna are known to the writer. 
Unfortunately little information is obtainable from the operations of 
the ‘‘Albatross,’’ for dredge hauls were not made between the dates 
of May 28 and October 15. None of the specimens collected at other 
times was examined with this in view. The reproductive period of 
Macoma nasuta, one of the most common bivalves, extends over a 
considerable portion of the year. This seems to follow from the fact 
that a number of living specimens less than ten millimeters in length 
were dredged during the months of January to May and again in 
October. 
It is presumed by Sumner et al. (1911, p. 178) that a considerable 
proportion of the marine invertebrates of Woods Hole reproduce in 
the winter. It is possible that the same statement would hold for the 
region of San Francisco, especially since the winter temperatures are 
much higher in these local waters. If the majority reproduce in the 
spring and summer, and if the low temperatures interfere with the 
reproductive functions and early development of the mollusk, the 
temperature factor should be recognized through a consideration of 
the distribution of the predominantly southward ranging species. 
In the following lists the predominately northward and southward 
ranging species are given for reference. 
PREDOMINANTLY NORTHWARD RANGING SPECIES TAKEN BY THE ‘‘ ALBATROSS’’ 
Acila castrensis Macoma balthica 
Acmaea patina Macoma inquinata 
Acmaea persona Macoma nasuta 
Adula stylina Macoma yoldiformis 
Amphissa corrugata Mangilia pupilla 
Calliostomia costatum Marcia subdiaphana 
Cardium corbis Melanella micans 
Cardium centifilosum Monia macroschisma 
Chrysodomus tabulatus Mopalia ciliata 
Cuspidaria californica 
Columbella gausapata 
Dentalium indianorum 
Entodesma saxicola 
Fissuridea aspera 
Hinnites giganteus 
Ischnochiton dentiens 
Kellia laperousi 
Lacuna porrecta 
Littorina planaxis 
Littorina scutulata 
Lyonsia californica 
Mopalia muscosa 
Mopalia wossenssenski 
Murex interfossa 
Murex lurida 
Mya arenaria 
Mya californica 
Mytilus edulis 
Mytilus californicus 
Nucula tenuis 
Nassa mendica 
Ostrea lurida 
Pandora filosa 
