REPORT OFT THE FORAMINIFERA. 
645 
That the peculiar features upon which the genus Asterigerina was originally founded 
prevail to a greater or less extent throughout the larger group of Rotalines which con- 
stitute the Discorbince of modern authors, is now generally admitted. Parker and Jones 
indeed go a step further, and associate the typical Asterigerina planorbis of the “ Vienna 
Basin ” memoir and the Rotalia rosacea of the “ Tableau Methodique ” as mere individual 
modifications of the same species. The difference between these two forms, as exemplified 
in the figures and model respectively, shows itself principally in the height of the spire, the 
former having a somewhat high conical test, the latter one of thin or more or less depressed 
contour. 
The variability of the species with regard to the size and prominence of the umbilical 
lobes or valves is illustrated by the drawings furnished herewith, fig. 1 representing a 
specimen in which they are but slightly developed, leaving a central open cavity, whilst 
in fig. 4 they are very conspicuous, alternating with the primary segments and covering 
the umbilicus. 
Discorbina rosacea is a common species. Within certain depths it is found in 
almost every sea, from the shores of Shetland and the Faroe Islands on the north to 
Mag-ellans Strait on the south. Its home is on shallow bottoms, and it becomes rare at 
greater depths than 250 fathoms ; but occasional specimens are met with as low as 
1000 fathoms. 
Its geological distribution commences with the Tertiary epoch. It occurs in the 
Eocene of Grignon, France (Parker and Jones) ; in the Miocene of various parts of the world 
(d’Orbigny, Parker and Jones, Seguenza) ; in the Pliocene of Italy (d’Orbigny, Seguenza) ; 
in the Crag of Norfolk and Suffolk (Jones, Parker, and Brady) ; and in the Post-pliocene 
of the British Islands (Shone, Robertson, Wright), and of the Island of Ischia (Vanden 
Broeck). 
Discorbina vilardeboana, d’Orbigny, sp. (PL LXXXVI. figs. 9, 12 ; PI. LXXXVIII. 
fig. 2). 
Rosalind vilardeboana, d’Orbigny, 1839, Foram. Amcr. Mbrid., p. 44, pi. vi. figs. 13-15. 
Discorbina 'vilardeboana, Parker and Jones, 1872, Quart. Journ. Geol, Soc., vol. xxviii. p. 115. 
Discorbina araucana, d’Orbigny, sp. (PL LXXXVI. figs. 10, 11). 
Rosalina araucana, d’Orbigny, 1839, Foram. Amer. Merid., p. 44, pi. vi. figs. 16-18. 
Discorbina araucana, Parker and Jones, 1872, Quart. Journ, Geol. Soc., vol. xxviii. p. 115. 
These are two out of a number of almost indistinguishable varieties of Discorbina 
of the “ rosacea ” type, which are widely distributed in both hemispheres. 
They occur in shallow water at almost every latitude, from the shores of Japan to 
Kerguelen Island and the coast of Patagonia. 
(ZOOL. CHALL. EXP. PART XXII. — 1884.) 
Y 82 
