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 L. lesueuri, and some varieties of the high form, 

 seem to be typical examples of L. 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 L. australis with this northern form. 



I have compared the contents of these six tubes with very numerous specimens 

 of L. 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 

 £i. australis. 



Meisenheimer (Siidpolar Exped. p. 106) regards L. 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. 



Clio sulcata, Pf offer. 



Pfeffer, Uebersicht der auf S. M. Schiff Gazelle gesammelten Pfcerpoden, Monatsb. k. preuss. Akad. Wiss., 



Berlin 1879, p. 240. 

 Pelseneer, ' Challenger ' Eeports, No. LXV., Thecosomata, p. 62. 



Two specimens labelled " 1. 1. '02. 63° 04' S., 175° 43' 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 



D 2 



