28 
PACIFIC SCIENCE, Vol. XVIII, January 1964 
the crab was the tiny amount of coloring be- 
tween the pinching fingers of the chelapeds. 
From our collecting and our field impressions 
we would say that this species is definitely more 
abundant in December and January than in the 
spring and summer months. However, it is 
also true that during these cold-water months 
the algae are practically absent from the pilings. 
Thus this crab is probably more readily observed 
in the absence of algae or other invertebrates. 
REPRODUCTIVE ACTIVITY: The nature of the 
hiding places used by S. acutifrons has made 
observation of reproductive activity, other than 
the possession of eggs by females, difficult to 
observe. Garth (1958:255) records collecting 
ovigerous females off southern California in 
every month but March, July, and September; 
and Way (1917:371) records taking two ovi- 
gerous females in July at Friday Harbor, Wash- 
ington. Ovigerous females were collected or 
observed during every month except April and 
May and September and October, when no speci- 
mens of Scyra were collected at all. There is no 
doubt that ovigerous females do occur during 
these "barren” months, since females with very 
new eggs were found just prior to these times. 
Moreover, females with extremely new eggs 
were collected during all of those months cited 
above and hatching was witnessed in the months 
of December and January, and June, July, and 
August. Results of 2 months of collecting will 
give an idea of the egg development encountered 
during different months of the year. During 
July, 12 of 17 females were ovigerous and, of 
the 12, 8 had extremely new eggs, one was of 
intermediate development showing eyes, and 3 
were in the hatching stage. In December, 29 
of 53 were ovigerous, with 25 having extremely 
new eggs, 3 well-advanced eggs, and one being 
in the hatching condition. Apparently there is 
no well-defined season of reproduction that gov- 
erns periods of quiescence and periods of repro- 
duction, although there is some suggestion that 
hatching may be confined to June through 
August and December and January. 
productivity: Eggs in egg masses of 12 
specimens of Scyra were counted. These speci- 
mens ranged from 19.5 mm to 30 mm in cara- 
pace width, and the egg mass size ranged from 
2,700 eggs to 16,300 eggs, with an average of 
8,600 eggs per female per brood. Dissections 
show that oogenesis occurs while the female 
has ova attached to the pleopods and thus a 
second brood may be produced very shortly after 
the current brood has hatched. 
family PORCELLANIDAE 
Petrolisthes eriomerus 
HABITAT: Petrolisthes eriomerus may be 
found in abundance in certain localities within 
the southern Puget Sound area. It was collected 
in large numbers in the Tacoma Narrows and 
at the Port Orchard collecting site. Smaller 
numbers were collected and observed at the 
eastern end of Titlow Beach and few specimens 
were observed at Point Defiance. Workers who 
have described the habitat of this animal con- 
sistently mention that they are found under rocks 
in the intertidal zone (Way, 1917:350; Hart, 
1930:105). Haig (1960:76) states that this crab 
occurs under stones in the lower part of the 
tidal zone in the northern part of the range, 
south to San Luis Obispo County, California. 
Both Way and Haig cite some deep collecting 
records for this species, but these records are 
predominantly for the southern extreme of the 
range, suggesting that isothermic temperature 
may be a partial key to the habitat of this crab. 
One habitat characteristic must always be 
present when these animals are to be found: 
there must be some current, however strong, 
which will bathe the habitat and will supply it 
with fresh plankton which is the chief source 
of food for this species. In all cases the number 
of specimens seemed proportional to the swift- 
ness of the current. The effect of a swift current 
on the habitat may be manifold: water is re- 
moved, food is carried into the habitat, and 
excessive debris is removed from the undersides 
of rocks. P. eriomerus is commonly seen clinging 
to the underside of rocks with its ventral side 
up towards the rock surface. When rocks are 
turned over numerous specimens are found 
clinging to the bottom. This species typically 
lives and feeds in this inverted position, using 
the tarsal hooks for holding onto rocks, or for 
locomotion. Without the protection of rocks 
these crabs right themselves and walk about on 
a sandy substrate in a normal manner. When 
these animals are dislodged and dropped into 
water they use the abdomen for locomotion. 
