376 
THE VOYAGE OF H.M.S. CHALLENGER. 
Spiroplecta americcma, Ehrenberg (PL XLY. fig. 24, a.b.). 
Spiroplecta americana, Ehrenberg, 1854, Mikrogeologie, pi. xxxii. I. figs. 13, 14; II. fig. 25. 
This species is distinguished from its congeners by the general contour of the test. 
The shell is usually much compressed, and widens rapidly towards the distal end ; the 
lateral edges are thin and slightly lobulated, the chambers somewhat inflated, and the 
septal lines correspondingly depressed on the exterior ; the walls are thin and smooth, and 
in small specimens hyaline. 
Spiroplecta americana has only been found living in one locality, off Paine Island, 
Torres Strait, depth 155 fathoms. 
The specimens figured by Ehrenberg were from the Cretaceous beds of Missouri and 
Mississippi, North America. 
Spiroplecta annectens, Parker and Jones, sp. (PI. XLV. figs. 22, 23, a.b.). 
Textularia annectens, Parker and Jones, 1863, Ann. and Mag. Nat. Hist., ser. 3, vol. xi. p. 92, 
woodcut, fig. 1. 
Under the name Textularia, annectens, Parker and Jones have described and figured 
a very long and slender variety of Spiroplecta, found by them in the Gault, which 
presents the trimorphous characters already referred to, owing to the addition of a variable 
number of uniserial segments to the normal dimorphous shell. 
The recent specimens figured in PL XLY. figs 22, 23, exhibit well the attenuated 
form of the test, and the characteristic arrangement of the chambers — planospiral at first, 
then biserial and alternate ; but they terminate in a single centrally-placed segment. 
Since these drawings were made, however, other specimens have been found, in material 
from the same locality, which have an addition of two or three uniserial chambers. The 
recent examples appear to be altogether more regular in contour than those from Cre- 
taceous sources, though they agree in essential particulars. 
Spiroplecta annectens is not uncommon at Station 185, off Raine Island, Torres 
Strait, 155 fathoms, and small specimens occur in a neighbouring locality, Station 192, 
off Ki Islands, 140 fathoms, but the species has not been found elsewhere. 
Parker and Jones state that it occurs, in company with other partially spiral Textu- 
larians, in the Gault of the south-east of England. 
Spiroplecta biformis, Parker and Jones, sp. (PI. XLY. figs 25-27). 
Textularia agglutinans, var. biformis, Parker and Jones, 1865, Phil. Trans., vol. civ. p. 370, 
pi. xv. figs. 23, 24. 
„ biformis, Brady, 1878, Ann. and Mag. Nat. Hist., ser. 5, vol. i. p. 436, pi. xx. fig. 8. 
This form is described by Parker and Jones ( loc . cit.), as “ a small Textularia with a 
sandy shell, often of a rusty colour, with scarce any shell-substance proper, — with a 
