PTEROPODA. 9 
If these forms were sharply distinguished from one another, they might be 
regarded as separate species, but in a few cases intermediate variations (fig. 7B) occur, 
such as a tall shell with deep sutures and seven whorls, of which the last is 
disproportionately larger than the others. Moreover, all the variations may be 
found in the same tube, which seems to show that they live together in their natural 
state. I think that the low form in ZL, lesweurt, and some varieties of the high form, 
seem to be typical examples of Z. australis. But if these forms pass into one another, 
and are not specifically distinguishable, they are not, in my opinion, specifically 
distinguishable from L. retroversa. Dr. Meisenheimer (Siidpolar Exped., p. 103) has 
already identified Z. australis with this northern form. 
I have compared the contents of these six tubes with very numerous specimens 
of Z. retroversa captured in the North Sea (where it seems to occur in vast quantities) 
and kindly lent me for examination by Prof. D’Arcy Thompson, C.B. The only points 
in which the whole series of Antarctic specimens can be said to differ from the northern 
specimens are the colour and surface of the shell. In the Antarctic forms it is 
opaque, not striated, and covered with a fine, irregular granulation ; in the northern 
form it is hyaline, transparent, and finely striated, the striae being composed of 
dots arranged in fairly regular, but not perfectly continuous, lines. These differences 
do not appear to me to have specific value. I can find no distinction in the breadth 
of the umbilicus or the obtuseness of the spire. Though L. retroversa is commonly 
said to have an acute spire, many of my specimens are quite as blunt at the tip as 
L. australis, 
Meisenheimer (Siidpolar Exped. p. 106) regards ZL. rangi and L.  lesueuri 
as separate species. I confess I doubt whether this distinction will be found to 
hold good, but the specimens now under consideration are certainly not L. rangi 
as defined by him, for the spire is higher, an accessory lobe is present on the fin, 
and the umbilicus is not particularly broad. 
Cio suLcaTa, Pfeffer. 
Pfeffer, Uebersicht der auf S. M. Schiff Gazelle gesammelten Pterpoden, Monatsb. k. preuss. Akad. Wiss., 
Berlin 1879, p. 240. 
Pelseneer, ‘ Challenger’ Reports, No. LXY., Thecosomata, p. 62. 
Two specimens labelled “1. 1. 702. 63° 04' S., 175° 48’ E.”, of nearly the 
same size and measuring about 18°5 mm. in length and 11°5 mm. in breadth. 
The shells are very fragile and both are broken, but they must have been about 
14°5 mm. long and 8 mm. broad at the top. When the animal is inside they are 
coloured rosy red by the viscera, but when empty are of a bluish white. The 
sides are inclined towards one another, and are not parallel in any part. There are 
lateral keels on the anterior portion of the shell, but they disappear before the 
D2 
