1918] Packard: Quantitative Analysis of Molluscan Fauna 307 
TABLE 2 
A REcorD OF THE Most PRODUCTIVE QUANTITATIVE Haut, Station D 5833 
Number Total Modal 
of living number of lengths 
individuals individuals in mm. 
Csiraiimy COMB TAD cuales sstureee-c.<2 pease 0 29 24 
Macoma balthica .. 128 127 15 
Macoma inquinata ... 0 7 38 
Macoma nasuta ..... 0 20 55 
Mya arenaria ..... 0 1 22 
Mya california ............ 2 7 11 
Mytilus edulis .............. 0 2 33 
Ostrea lurida .... 0 many St 
Paphia staminea ....... 1 3 10 
Schizothaerus nuttalli ree 0 fragm. 
MEN SO BIG OA OU shatter cnonpacest stsceenccenaereecnce 0 fragm. 
G@rrapxe ules MVC 8 eceacsnescsncsseteceseesecenrore 0 fragm. ae 
Epitonium hindsi ..... 128 128 3 
Epitonium sawinae ... 0 1 wie 
Nassa fossata ..... 0 1 22 
Mars Wamelll OSB) eee -ecceecacecenen 0 14 13 
It is of interest to note the average size of a few of the prevalent 
species. Such data are tabulated below. 
TABLE 3 
Tue AVERAGE SIZE OF THE LIVING SPECIMENS OF FIVE PREVALENT SPECIES 
Maximum 
length of 
Average living 
length of specimens 
specimens obtained in 
Species Number of for all hauls same hauls 
specimens in mm, in mm. 
Macoma nasuta 59 20 55 
Cardium corbis 11 9 17 
Mytilus edulis 4 8 17 
Mya arenaria 33 25.8 80 
Mya california 573 9.5 17 
The averages as given above are rather low, due in part to the 
relatively large numbers of very young individuals. These figures, 
however, combined with those given elsewhere in this paper, make it 
possible to picture the mollusean life of a typical unit area, besides 
giving the approximate numbers and dimensions of the individuals 
living within such an area. It is also possible to estimate roughly 
the amount of organic matter represented by the mollusks, after once 
having established the average number and size of the individuals 
per unit area, and the ratio of the organic to that of the inorganic 
matter for each species. 
A picture of the mollusean life of an average unit area, such as 
would be covered by the jaws of the orange-peel bucket dredge (7.8 
square feet), may be obtained from a consideration of the data pre- 
sented above. 
