44 
PACIFIC SCIENCE, Vol. XIV, January I960 
pearance which prove the identity of both forms 
are the colored stripes on the wall and the shape 
of the opercular valves. The shell is glossy white, 
smooth, and furnished with dark violet longi- 
tudinal stripes not crossed by any transverse 
stripes, though growth lines are faintly defined. 
Usually a broad white area is present in the 
middle of the larger compartments (carina, 
laterals, and rostrum), and a similar white area 
is present along both sides, the colored stripes 
being indistinct or quite absent there ( see Table 
1). The parietal tubes (the number of which 
corresponds with the number of the colored 
stripes, both distinct and obsolete) are narrow 
and numerous; the longitudinal septa on the 
inner lamina are strongly developed and run up 
to the sheath as high ridges which are very finely 
denticulate on both sides. The radii are very 
broad, with summits almost parallel to the base 
(Fig. 1). 
In describing the new variety denticulata 
from the Suez Canal, Broch (1927) did not 
mention its close affinity with his earlier form 
hawaiiensis described in 1922. A comparison of 
his descriptions and figures of both forms with 
the Japanese specimens of hawaiiensis clearly 
shows that there is no difference important 
enough to separate them as different subspecies. 
Therefore, I believe that denticulata must be the 
same as hawaiiensis. 
DIFFERENCES BETWEEN SUBSPECIES hawaiiensis 
AND subspecies communis 
Notwithstanding the peculiarities mentioned 
above, sometimes there has been confusion 
among cirripede systematists between forma 
hawaiiensis (or denticulata ) and Darwin’s vari- 
ety communis ( see Table 3 ) . 
For example, Nilsson-Cantell (1938: 37) 
recognized both subspecies as distinct, but men- 
tioned that "I do not consider it impossible that 
they ( denticulata ) represent a special race from 
the canal zone, but I do not think that numerous 
teeth on the labrum are a special characteristic 
of the subspecies denticulata !’ He emphasized 
that a great variability in the number of teeth 
on the labrum is not always of systematic im- 
portance, remarking that "the typical communis 
also has numerous teeth on the labrum.” How- 
ever, I most emphatically dissent from his 
opinion in this respect. As he says, it is true that 
the balanids are highly variable as far as a par- 
ticular character is concerned, but I hold that 
there are certainly some admittable limitations 
in the range of variation. A similar unreliability 
in identifications based only on the labrum was 
pointed out by Pilsbry (1916: 88), in the case 
of Balanus improvisus. 
Some specimens of subspecies communis re- 
semble subspecies hawaiiensis superficially, be- 
ing often found together in the same place, but 
TABLE 1 
The Number of Longitudinal Colored Stripes in all Compartments of Balanus amphitrite 
hawaiiensis AND Balanus amphitrite communis* 
SIZE OF 
SPECIMENS 
CARINA 
LEFT 
CARINO- 
LATERAL 
COM- 
PART- 
MENT 
RIGHT 
CARINO- 
LATERAL 
COM- 
PART- 
MENT 
LEFT 
LATERAL 
COMPART- 
MENT 
RIGHT 
LATERAL 
COMPART- 
MENT 
ROSTRUM 
B. a. hawaiiensis 
c.r.d. 15.4 mm. 
(0)5(1)50) 
(1)2(1) 
(0)2(2) 
0)4(2)40) 
(0)50)4(2) 
(2)5(2)5(2) 
c.r.d. 18.0 mm. 
(1)3(2)4(1) 
(1)2(1) 
(1)2(2) 
(2)4(2)40) 
(05(2)4(2) 
(2)5(3) 6(1) 
c.r.d. 18.5 mm. 
(0)5(2)4(0) 
(0)3(1) 
(1)2(1) 
(2)50)3(1) 
(1)40)4(0) 
(2)4(2)4(3) 
c.r.d. 19-6 mm. 
(2)4(1)30) 
(1)2(1) 
(1)2(1) 
(1)30)4(2) 
(2)2(2)2(0) 
(05(2)4(2) 
B. a. communis 
c.r.d. 14.0 mm. 
10 
3 
2 
10 
9 
9 
c.r.d. 18.2 mm. 
8 
2 
2 
9 
9 
9 
c.r.d. 20.0 mm. 
9 
4 
2 
10 
10 
10 
* c.r.d. = carino-rostral diameter. Numbers without parentheses represent distinct stripes. Numbers in parentheses represent 
obsolete or reduced stripes. The total number corresponds with the number of parietal tubes in each of the compartments. 
