302 
Proceedings of the Royal Society 
The Head is short and broad ; the eyes prominent. 
The Arms are subequal, their order of length being 4, 3, 1, 2 ; 
they are about one-fourth as long as the body and taper to fine 
points : the dorsal are conical with a very slight ridge up the 
outer aspect, the third pair have a similar ridge ; the ventral are 
flattened and bear a distinct crest. The suckers are in four series 
throughout and of moderate size, set obliquely on short peduncles, 
with meridional grooves on the outside : the horny ring bears 
twenty to twenty-five long, square-cut, irregular teeth in its distal 
semicircumference, and outside it is an area covered with close-set 
papillae. The liedocotylus is not developed. The umbrella is 
slight, reaching only as high as the sixth row of suckers between 
the third and fourth arms, where it is widest ; as usual it is 
entirely absent between the two ventral arms. The buccal membrane 
has the usual seven points. The spermatic cushion is not developed • 
the outer lip is smooth, except for a few ridges due to contraction ; 
the inner bears numerous small papillae. 
The Tentacles are about as long as the body, the stem being 
three-sided : the club is short, flattened, and expanded, with a 
protective membrane on either side and a broad web down the 
back, reaching along the stem for a distance equal to half the 
length of the club ; it bears six larger suckers in the central line, a 
series of smaller ones on either side, and some very minute ones 
along each margin : at the top are fifteen to twenty in four series. 
The horny ring of the large suckers has twenty-five to thirty 
teeth in its distal semicircle ; those of the smaller about ten. 
The Surface is smooth, except for a few irregular inconstant 
papillae on one side of the ventral surface and below the eye. 
The Colour is a pale yellowish grey, darker above. 
The Shell is oval in outline , broadest anteriorly to the middle, 
tapering somewhat rapidly in front and ending in a semicircle ; 
posteriorly it tapers gently, and, then rounding off, ends in two 
almost straight lines, which meet at a right angle at the base of the 
spine. The chitinous margin extends but slightly over the dorsal 
surface , which shows two grooves diverging as they pass forwards, 
separating three ribs, and is covered with rounded papillae arranged 
in curves parallel to the anterior margin. The ventral surface has 
a rather deep and broad median groove : the last locidus occupies 
