NO. 3594 SARSIELLA — KORNICKER 7 



molts (Przibram, 1931, p. 21), il is possible to conclude that instars I 

 and II are missing from the collection. The conclusion, however, 

 must be considered tentative because of the many factors that cause 

 the growth rate to deviate from the theoretical (Teissier, 1960, p. 

 541). Males of instars I and II are also missing from the collection. 

 Lateral outlines of shells at stages of development present in the collec- 

 tion are illustrated in figure 2. Average dimensions at each growth 

 and calculated growth factors of females from California are tabulated 

 as follows: 



growth stage average length grotvih factor average height growth factor 



(mm) (mm) 



adult 1.24 1.11 



1.34 1.41 



V 0.92 0.79 



1.33 1.33 



IV 0.69 0..59 



1.23 1.29 



III 0.56 0.46 



1.26a 1.26" 



II (missing) 0.44^ 0.36'' 



1.26" 1.26" 



I (missing) 0.35b 0.29^ 



embryo (from Mass.) 0.32 0.26 



» Przibram's tlieoretical growth factor for a linear dimension. 



b Calculated dimensions estimated by dividing Przibram's factor (1.26) into dimension of succeeding 

 growth stage. 



In several collections off Point Richmond, Calif., Jones (1961, 

 figs. 20d-g) obtamed a total of al)out 240 adiJt females and 36 adiJt 

 males; adidt females outnumbered adult males by 6 or 7 to 1. In 

 the present study juveniles were picked at random from available 

 collections from Point Richmond. The numbers are too few to 

 determine accm'ate ratios; however, females outnumbered males in 

 all molt stages: 



Description of adult female. — Shell (figs. 3a, b; 4; 5a-d; pi. 1) : 

 dorsal view with broadly rounded posterior and acimiinate anterior 

 (fig. 36) ; oval in lateral view except for postero ventral caudal process 

 (figs. 3a, 4a). Surface ornamented with pmictae and 3 raised ribs 

 radiating from hub slightly forward of center of valve; posterior rib 

 terminating in knob with 2 small lateral pits; velate ridge parallel 

 to edge of valves; shell broadest at hub of radial ribs or at pitted 



