Pacific Salpidae — YoUNT 
297 
in the dorsal longitudinal muscle extension. 
The difference described in the ventral ex- 
tension is perhaps only one of growth. At 
any rate, it is rather minor. 
5. In Ihlea asymmetrica sol. there are lateral 
projections on either side of the gut in em- 
bryos (and the small specimen of Ihle, 1912), 
whereas these have not been reported in /. 
punctata (Apstein, 1901, Ihle, 1912, and Met- 
calf, 1918, have reported them in /. asym- 
metrica). As Metcalf (1918) pointed out on 
his embryo, lateral projections are probably 
only embryonic attachment organs. Thus they 
may disappear in adults. They are presumably 
present in embryos of both so-called species. 
6. In /. punctata sol. there are pigmented 
areas on the lips and posteroventral region 
near the gut (Metcalf, 1918), whereas these 
have not been reported in 1. asymmetrica. 
Again, the presence or absence of pigment is 
probably largely determined by the length 
of exposure to preservation fluid. 
7. In I. asymmetrica sol., the bow muscle 
(C) and I, II, III, and IV form one group 
dorsally, M VII, VIII, and x form another 
(Metcalf, 1918); or C-I-II form one group, 
III-IV form another, and M VIII and x form 
a third group (Apstein, 1901); or C-I-II form 
one group dorsally, M III-IV a second, and 
M VII-VIII-x form a third group (Ihle, 1912) . 
On the other hand, in I. punctata C-I-II form 
the only group (Traustedt, 1893); or all re- 
main separate (Apstein, 1906^,^; Streiff, 
1908); or C-I-II form one group, and VII 
(?)-VIII-x (figures of Metcalf, 1918) form 
another. These differences in muscle group- 
ing are probably only individual variation and 
are considered nonuseful here. 
As a result of an exhaustive review of the 
literature, I can conclude only three possibil- 
ities: (1) the two species may be distinct, but, 
if so, the descriptions are in such a tangle 
that they are in large part unreliable; (2) the 
two so-called species are one, the differences 
described being due only to individual varia- 
tion, not to specific, subspecific, varietal, or 
formal variation; (3) the two species are one, 
the differences described being due to varia- 
tions important enough, perhaps, to consider 
1. asymmetrica to be only a form or variety of 
the main species, 1. punctata. This form would 
be distinguished from the main species only 
by the length of the ventral longitudinal mus- 
cle and the absence of pigmented areas in the 
test. 
It is my opinion that possibility 2, above, 
is the correct one. Therefore, the two species 
are here regarded as only one, Ihlea punctata 
{ = 1. asymmetrica), with no differences other 
than what can be attributed to individual 
variation. 
This conclusion is upheld by an embryo 
(solitary form) in the POFI collections. This 
embryo’s ventral longitudinal muscle extends 
up to the anterior edge of M IV (a character 
of I. punctata, presumably) ; it also, however, 
possesses attachment organs— one on each 
side over M x (a character of 1. asymmetrica, 
presumably). 
Genus Salpa Forskal, 1775 
Solitary form with eight ventrally inter- 
rupted body muscles, aggregate form with 
six. In the aggregate form, these muscles form 
two groups dorsally. Transverse ridges of gill 
bar taper gradually to a point ventrally and 
are separated from one another by a distance 
less than 0.5 the width of the gill bar. 
Two species, Salpa maxima (type) and S. 
fusiformis. 
Salpa fusiformis Cuvier, 1804 
Figs. 11^-^, 12^-^, 15^, 16^ 
Salpa fusiformis Cuvier, 1804: 382; Bomford, 
1913: 243; Ihle, 1935: 527-529; Tokioka, 
1937: 223; Thompson, 1948: 156; Berrill, 
1950: 293. 
Salpa aspera Chamisso, 1819: 14. 
Salpa runcinata Chamisso, 1819: 16. 
Biphora depressa Sars, 1829: 51. 
Biphora tricuspidata Sars, 1829: 56. 
Salpa clostra Deshayes, 1836-46: vol. 121, figs. 
2-2a. 
