KUNGL. SV. VET. AKADEMIBNS HANDLINGAR. BAND 52. N:o [6. 19 
LINNE says (Syst. Nat. X, p. 705), whitish, with some violet flames towards the um- 
bones and some traces of a reddish-yellow tint at the ventral side, originally spread 
over this region. Its posterior and dorsal part is reddish brown, darker towards the 
margins. The interior is white in front and below, violet with a slight margarit- 
aceous hue for the chief part, and reddish brown along the dorsal and posterior 
margins. 
The original sculpture still appears clearly towards the margins (fig. 1 a) which 
are finely crenelated all round with fine and dense radiating lines entirely covering 
the shell. 
The interior septum (fig. lc) is rather broad (its breadth exceeding its height) 
and of a white colour. Its inner edge is slightly concave below and has in its 
upper half an almost obsolete convexity, which is situated half-way between the umbo 
and the posterior end of the ligament; the edge passes — describing a very slight 
sinus — into a comparatively short subligamental crest. From the ligament furrow 
the shelf is separated by a slight rib, which runs from the hindermost tooth, tapering 
backwards. 
There are three teeth in the left valve, the median of them being the largest, 
as well as the rear one in the right valve. These each form a somewhat irregular 
knob with two or three smaller swellings. 
The present Australian form differs from the typical specimen of S. bilocularis 
in having a more attenuated umbonal part and a septum which is longer than it is 
broad, and has, generally, in its upper half, a distinct prominence, which is situated 
nearer to the umbo than to the posterior end of the ligament. Further, the shelf is 
not limited from the ligamental furrow in the same manner as in the type. The 
teeth are about three in number in each valve, and vary much in form and position. 
These characteristics, as well as the white colour of the shelf, seem to be fairly con- 
stant in the Australian form, judging from the material at my disposal. Whether 
they are so important as to justify us in distinguishing the present form as a 
distinct species is a question that I cannot decide, since I lack sufficient material of 
the typical form for judging of the constancy of the characteristics of the Linnean 
specimen. I think that the Australian form must at least be considered a special 
variety in the same respect as the Indian and Japanese form, which is characterized 
by a constantly bluish green septum, with a tooth-like projection of the edge. 
Modiola philippinarum Hanituy. 45 miles W. 8. W., 72 feet (1/7), 1 sp., 1. 65 
mm; 80 feet (*°/s), 1 sp., 1. 6.3 mm. The first specimen is like MW. albicosta LAMARCK 
but differs in its somewhat sharper prominent lines of growth and more stretched 
upper margin, and it agrees with fig. 1 in ReEve (Conch. Icon. 10, 1858). In the 
second specimen the cuticular hairs are scanty, elongated, with short distant 
branches. The colour is red with a white costa. From M. plumescens it differs in 
its higher, rising upper margin and in its sharp concentrical folds, which are obsolete 
in front and begin to appear on the diagonal costa. Distribution: Red Sea and Per- 
sian Gulf to Japan, Torres Strait and Queensland (Lyne@e 1909); W. Australia 
(HEDLEY 1916). 
