136 I^I- SASAICI. 
The tubercular scries of the dorsal surface of the mantle is not quite 
median in position, but deviates into the ri<^ht side posteriorly. It begins at 
the projected middle point of the anterior margin of the mantle, and runs 
straight backwards for some distance ; then it curves gradually into the 
right side, almost reaching the anterior end of the attachment of the right 
fin. Tlie tubercles are not so many as thirty, as in M. hoyki, but only seven- 
teen and are small, being nearly of ecjual size. 
The luminous organs are uniform in appearance, thickly covering the 
ventral surface of the whole body and are found in less number on the dorsal 
surface. 
On the ventral surface of the mantle, they are thickest in distribution at 
the anterior region, becoming thinner and diminishing in size towards the 
posterior end, and they show a regular arrangement in an oblique direction 
at the anterior half of the mantle. The most anterior transverse row along 
the edge of the mantle-opening consists of about thirty-eight organs, but of 
these only about twenty-five are visible from the ventral side. And when they 
are counted longitudinally along the median line of the ventral surface, though 
they do not show a quite regular series, the number is about twenty-four. 
The dorsal surface of the mantle is provided with a small number of the 
organs, which show a most irregular arrangement and are asymmetrical in 
distribution on both sides, those of the left side being a little thinner in dis- 
tribution and smaller in size than those of the right side. When the mantle 
is seen from the right side, the organs show a quite regular arrangement, the 
series diverging somewhat from the median part of the ventral anterior 
margin towards the posterior dorsal direction. 
The ventral surface of the head is also thickly covered with organs ar- 
ranged in oblique series. The most posterior transverse row along the an- 
terior boundary edge of the neck consists of twenty-four organs, which is 
thickest in arrangement in the middle. The number of the organs in the row 
between both the eye-openings can not be counted, on occount of the skin 
being torn, but judging from the arrangement of the anterior as well as the 
