MARINE MOLLUSCA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 121 



species of Margarita. To us, and several other malacologists who have examined it 

 with care, it not only appears almost full-grown, hut with some confidence is now pro- 

 posed to be included in the genus Cyclostrema, at all events provisionally ; for this 

 genus is somewhat multifarious already in its component parts, and much needs the 

 services of a special monographer. 



The nuclear whorls are, it is true, slightly nepionic. and shapelessly turgid, but the 

 penultimate and body whorls are very well sculptured and defined, being acutely spirally 

 bicarinate. Around the umbilicus, likewise, a third keel, crenulate, and not so acute, 

 revolves. A pale straw-coloured epidermis covers the whole surface uniformly. The 

 operculum, for microscopic aid in the examination of which we are much indebted to 

 Messrs E. A. SMITH and ROBSON of the British Museum (Natural History), is dark red- 

 brown, with nucleus not quite central, and multispiral. This we take the opportunity 

 also to figure (fig. 22a). 



Calliostoma modestulum, Strebel. 



Calliostoma modestulum, H. Strebel, Schwed. Sudpolar Exped., p. 70, Taf. i. fig. 13 a, b (1908). 



Hab. Station 346, Burdwood Bank, 56 fathoms, from Sponge. 



Two very young specimens, trochoid in form, with the upper whorls elegantly 

 spirally lirate, we assign to the above name with a little doubt. The original type 

 came from the West Falklands, lat. 52 29' S., long. GO" 36' W., dredged at 197 metres 

 (STREBEL). 



With this occurred Photinula expansa, Sowb. , and one broken example of a 

 beautifully nacreous shell, which, judging from the figure,* may be Calliostoma 

 mobiusi, Strebel. Our specimen is more trochoid than photinuloid, though it possesses 

 some characters of the latter, and is lightly spirally grooved, these being most con- 

 spicuous at the periphery of the body whorl. Dimensions : alt. 10, diam. 12 mm. It 

 likewise may be compared with Photinula Crawshayi,^ Sm., from Christmas Island, but 

 the whorls are not ventricose. It is unfortunately somewhat broken ; the operculum is 

 present, being horny and multispiral. 



Sub-order MONOTOCARDIA. 

 (a) Ptenoglossa. 

 Family Scalidse. 



Scala magellanica, Phil. 



Scalaria magellanica, Pliilippi, Archiv fiir Nnfunj., vol. i. p. 65 (1845). 

 Hab. Station 346, Burdwood Bank, 5<> fathoms, in Sponge. 



Only very imperfect specimens, either very young or broken fragments; enough, 

 however, to identify the species. 



* STREBEL, Mnll. <lcr Maynlhcien. Prov., ii. p. 133, Taf. v. fig. 22. 

 t SMITH, Proc. Malac. Soc. Land., vi. p. 335, fig. 2. 



(ROY. SOC. EDIN. TRANS., VOL. XLVIII., 347.) 



