410 
THE VOYAGE OF H.M.S. CHALLENGER. 
Just at its commencement the test is planospiral ; but with this exception, it is formed 
of two oblique nearly parallel series of segments, exactly as described by Prof. Williamson. 
Unfortunately the original drawings of this species ( loc . cit.), do not show the segmenta- 
tion of the test at all clearly, probably because the specimens themselves were wanting in 
definition, and guided by them Dr. Carpenter has been led to the conclusion that “ the 
later segments present a uniserial rectilinear succession ” (Introd. Foram., p. 195), which is 
certainly not the case in the examples that have come under my notice. It appears to 
me open to doubt whether the form has not more in common with the partially uncoiled 
Cassidulince than with the present genus the few specimens which I have examined 
suggest rather than decide the question. 
Bulimina convoluta is a very rare Foraminifer. The Challenger specimens are from a 
single Station, — the rich sounding off Raine Island, Torres Strait, depth 155 fathoms; 
Williamson’s were from Shetland and Skye ; and the Rev. A. M. Norman has good 
examples from two points on the coast of Norway, namely, — off Stoksund, 126 fathoms, 
and off Sartoroe, near Bergen, 40 fathoms. These five localities embrace all that is 
known of its distribution. 
Pleurostomella, Reuss. 
Pleurostomella, Reuss [1860], ScL wager, Gumbel, Hantken, Wright, Marsson, Moore, Berthelin, 
Brady, Terrigi. 
The genus Pleurostomella was established by Reuss for two subcylindrical forms of 
Foraminifera found in the Cretaceous beds of Westphalia. 1 These, which though 
separately named probably belong to the same species, resemble irregularly built 
Nodosarians, the one curved or Dentaline, the other straight. The chambers are 
numerous and joined end to end, but their sutures are oblique and in a certain sense 
alternating, that is to say, inclined first towards one side and then towards the other. 
The segments are disposed in single series, and except just at the commencement of one 
of the specimens, there is no approach to true Textularian arrangement. Guided by the 
contour of the individual segments and the apparent plan of growth, the genus was 
originally placed by Reuss in a family by itself, at the end of d’Orbigny’s Order 
Stichostegia, immediately following Vaginulina ; and in his own subsequent classification 
of the Foraminifera, the Pleurostomellidea were assigned to the Rhabdoidea. 2 In either 
case the type was treated as one having close affinity to the Nodosarince. 
But in many ways the Cretaceous specimens on which the genus was founded do not 
fully represent its characteristic features. These were first brought into notice by the 
beautiful drawings accompanying Dr. Schwager’s memoir on the fossil Foraminifera of 
1 Sitzungsb. d. 7c. Ah. Wiss. Wien, vol. xl. p. 59, pi. viii. figs. 1, 2. 
2 Ibid., vol. xliv. pp. 368, 395. 
