314 DISCOVERY REPORTS 



characteristic of the M. semimiliim group in the Falkland Islands material. O. araucana 

 (d'Orbigny) which was recorded by that author only from Valparaiso, on the Chilean 

 coast, and which differs from O. mogellanica mainly in its narrower outlines and less 

 acute peripheral edge, occurs but very rarely, the best being at WS 86, io8 and 221 (see 

 Plate VI, figs. 28-30). The Types of O. araucana are deeply stained with iron, but the 

 sutures are very strongly marked and we have no doubt that they are in general agree- 

 ment with d'Orbigny 's figure. Ouinqiielocidina isabellei is characterized by a more 

 compressed shell with inflated chambers and depressed sutures. We have notes of its 

 occurrence at six stations only, viz. 388, WS 87, 88, 90, 91, 93. It is probably more 

 widely distributed but escaped observation. The Type was not to be found in Paris. 



Among the Paris Types the tube labelled " O. magellanica, lies Malouines ", contains 

 nine large Miliolids in good condition. Some of them are in agreement with d'Orbigny's 

 figures, but the others cover a wide range of variation within the species M. semimilum, 

 including the sigmoiline form referred to below. One of the specimens is nearer 

 M. vulgaris than M. semimilum. 



Among our specimens a form with somewhat recurved angular edge suggesting a sig- 

 moiline structure arrests attention (Plate VI, figs. 31-3). It was at first assumed to be a 

 Sigmoilina, although its general resemblance to M. seminulum and its constant association 

 with that species brought it under suspicion. Its MilioHne nature having been established, 

 it seemed probable that it would prove to be the microspheric form of that species, in view 

 of the fact that Schlumberger in his sections of M. seminulum (S. 1893, MGM, p. 67 

 [in the reprints, p. 209], figs. 15, 16) indicates a similar "pseudo-sigmoiline" curve in the 

 external wall of the microspheric form. But a series of sections has proved the existence 

 of both megalospheric and microspheric individuals in each form, the latter as usual 

 being very uncommon (Plate VI, figs. 37-40). The megalosphere of the angular 

 sigmoiline form appears to be invariably smaller than in the normal M. seminulum, 

 and it seems probable that the species exhibits the "trimorphism" of Hofker, or 

 "polymorphism", as has been alternately suggested for the phenomenon. 



The best specimens of the sigmoiline form were obtained at 388 and WS 84, where 

 large and highly polished individuals are common. 



Goes in his Arctic and Scandinavian Foraminifera (G. 1894, ASF, p. 108, pi. xviii, figs. 

 838 c, d) gives sections of the two forms of M. seminulum, which, although less distinctive 

 than Schlumberger 's so far as external characteristics go, bring out what he regarded as 

 a " sigmoiline " arrangement of the chambers in this species. Our own sections seem to 

 prove that, while the microspheric form is distinctly sigmoiline in the arrangement of its 

 chambers, no similar curve can be made out in the megalospheric form. 



13. Miliolina patagonica (d'Orbigny) (Plate VI, figs. 10-12). 



Quinqueloculina patagonica, d'Orbigny, 1839, FAM, p. 74, pi. iv, figs. 14-16. 

 Three stations: WS 83, 217, 245. 

 The occurrence of d'Orbigny's little form at these stations is worth recording, 



