134 "TERRA NOVA" EXPEDITION. 



(Hector), 1887 (Withers, P.Z.S., 1913, p. 840, pi. LXXXV), differing from it, however, 

 in the following particulars : — 



1. In the rostrum, the lateral strips marked with longitudinal lines extend to 

 the base. 



2. In the laterals, the ala is relatively wider, and the internal sculpture is a little 

 different, the lines of the parietal margin lacking the downward bend where they meet 

 the longitudinal ridge, and the transverse lines of the ala being stronger. 



3. In the carino-laterals, the internal sculpture shows the same features as that of 

 the laterals. 



4. In the carina, the angles of the alae are nearer the apex of the valve, and the 

 transverse sculpture of the inner side is stronger and more extensive. 



The tergum and scutum are shown in Figs, le, e', f, f. The longest valve, a carina, 

 would measure, if complete, nearly 90 mm. The rest are of the same order of magnitude. 



The occurrence of this barnacle presents a very puzzling problem. It is not 

 possible to judge from the appearance of the shells whether they are recent or fossil. 

 The valves are all disarticulated, of a pure and brilliant whiteness, and without any 

 trace of organic matter, but they are not imbedded in any matrix. They are covered 

 with a very fine white dust, but this may be derived from the disintegration of their 

 surface, though they are sharply sculptured, and retain Sjyirorbis shells that have 

 o-rown upon them on iDoth inner and outer surfaces. More probable traces of a matrix 

 are minute sandy deposits which soil the surface here and there, but the meaning 

 of these is doubtful. That the animals should be recent seems, however, hardly 

 possible, for no trace of such a barnacle has been found in any dredging or collection 

 either in the Ross Sea or elsewhere, nor — a stronger argument — can any satisfactory 

 suggestion be made as to the way in which recent shells could have reached the position 

 in which these were found. The nearest known relation of H. antarcticum is H. 

 aucklandicum from the Miocene of New Zealand. The other described members of 

 tlie genus are recent deep-sea species of small size. Withers thinks that the loose 

 articulation and relative thinness of the shell of H. aucldandlcum shows that it also 

 lived below the littoral zone. The shell of H. antarcticum is similarly loosely 

 articulated, though it is not particularly thin. If the new species be a fossil, it seems 

 hio'hly probable that it is, if not of Miocene age, at least Tertiary, for it is quite unlike 

 any Cretaceous barnacle. Here, however, is the difhculty. No Tertiary rocks are 

 known from the neighbourhood of the glacier in which the shells were found, nor, 

 indeed, has anything later than the Carboniferous been reported in this region. It may 

 be that somewhere in its course the glacier is in contact with Tertiary rocks. Decision 

 upon this point must rest with the geologists. It is for them also to decide what 

 bearing the facts here stated may have upon the history of the Antarctic Continent.* 



* Hennig (Wiss. Ergebn. Schwed. Siidpolar-Exped. Ill, X, p. 10, pi. XI, figs. .3-7, 1911) mentions 

 the existence in the Pleistocene of Cockbui-n Island of a small Balanus, but this is quite unrelated to 

 Hexelasma antarcticum. 



