570 
THE VOYAGE OF H.M.S. CHALLENGER. 
separated by excavated sutures. It is not to be confounded with the Polymorphina lactea, 
var. oblonga, of Williamson, which has an oval compressed shell with erect segments and 
flush sutures. 
The distribution of Polymorphina oblonga, whether geographical or geological, is 
similar to that of the allied forms already named, with which indeed it is generally found 
associated. It seldom occurs at greater depth than five hundred fathoms, but the 
fistulose modification has been met with at one point in the North Pacific as low down as 
2050 fathoms. 
Polymorphina rotundata, Bornemann, sp. (PI. LXXIII. figs. 5-8). 
Guttulina rotundata, Bornemann, 1855, Zeitsebr. d. deutsch. geol. Gesellsch., vol. vii. p. 346, 
pi. xi. pi. xviii. fig. 3. 
55 
incurva, 
Id. 
Ibid. 
p. 345, pi. xvii. fig. 6. 
55 
fracta, 
Id. 
Ibid. 
p. 344, pi. xvii. fig. 4. 
55 
dimorpha, 
Id. 
Ibid. 
p. 345, pi. xvii. fig. 5. 
Polymorphina tenera, Karrer, 1868, Sitzungsb. d. k. Akad. Wiss. Wien, vol. lviii. p. 174, pi. iv. 
fig. 9. 
Rostrolina, sp., Scblicbt, 1870, Foram. Pietzpnhl, p. 72, No. 412, pi. xxvi. figs. 13-15, &c. 
Polymorphina rotundata, Reuss, 1870, Sitzungsb. d. k. Akad. Wiss. Wien, vol. lxii. p. 487, 
No. 14.- — Schlicht, op. cit., pi. xxvi. figs. 13-15; pi. xxviii. figs. 1-5; pi. xxx. 
figs. 33-40. 
„ turgida, Id. Ibid., p. 487, No. 10. — Schlicht, pi. xxviii. figs. 6-10 ; pi. xxix. figs. 1-5. 
„ rotundata, Brady, Parker, and Jones, 1870, Trans. Linn. Soc. Lond., vol. xxvii. p. 234, 
pi. xl. fig. 19 a-e, and woodcuts. 
This is an exceedingly variable form, and one which it is almost impossible to 
describe in definite zoological terms, though it exhibits a certain habit of growth that is 
seldom difficult to identify. Eeferring to the illustrations, — figures 7 and 8 are drawn 
from nearly typical examples ; and between these and extreme varieties like figures 5 
and 6, specimens exhibiting every gradation of contour and structure are met with 
wherever the species abounds. Of such individual modifications Bornemann ( loc . 
cit.), makes several “ species but the still larger array of drawings furnished by von 
Schlicht are grouped by Reuss under only two names, Polymorphina rotundata and 
Polymorphina turgida. Between the latter I can find no serviceable mark of distinction, 
taken together they form a natural and convenient quasi-specific group. 
Polymorphina rotundata is not common in the living condition. A few specimens 
have been collected in the British seas, off the west coast of Scotland (Robertson) and 
the north-east of Ireland ; and in the Mediterranean, off Malta. It occurs more plenti- 
fully in the Southern Ocean, off Prince Edward Island, 50 to 150 fathoms ; also at one 
Station in the North Pacific, depth 1850 fathoms ; and at one in the South Pacific, 1825 
fathoms. 
