636 
THE YOYAGE OF H.M.S. CHALLENGER. 
The test is Rotaliform ; the arrangement of the segments is always spiral to begin 
with, but frequently annular or irregular during the subsequent stages of growth ; and 
(typically) the individual segments open directly into a central umbilical cavity or 
vestibule on the inferior side. The successive chambers are not closely contiguous, but 
are separated by intervals, which appear on the inferior face in the form of radiating 
depressions or fissures. In certain cases the base of the shell is enveloped by a distended 
balloon-shaped chamber. The general contour of the test is either conical, convex, 
complanate, or, as in the variety last referred to, subglobular. The fossil representatives of 
the type attain a diameter of -^th inch (l - 4 mm.), the recent species are scarcely so large. 1 
Broadly speaking, the foregoing are the salient features of the genus, the most dis- 
tinctive being the independent communication of the individual chambers with the 
umbilical vestibule, and the separation of the successive chambers by depressions or 
intervals. The latter peculiarity often produces an appearance of alternation in the 
arrangement of the adjacent annuli. There are other points of interest, both structural 
and morphological, but as they are for the most part of specific rather than generic 
application, their consideration may be deferred. 
The genus Cymbalopora is classed by Carpenter and his colleagues with the Rotalina:, 
by Biitschli with Globigerinina;; in point of fact, it has intermediate characters which give 
it almost equal claim to rank with either group. In many respects it betrays an affinity 
to Discorbina, but its closest relationship is undoubtedly with the Planorbuline series 
and with Patellina ; it has therefore been retained in the position assigned to it by the 
former authors. 
The geographical distribution of the genus is limited to tropical and subtropical 
latitudes. It reaches as far north as Bermuda and the Azores, but in the southern 
hemisphere it has not been met with south of the Friendly Islands, which are just within 
the tropical line. Its home is amongst coral-sand, and it is found at every depth from 
the littoral zone down to 600 or 700 fathoms. The best-known fossil Cymbalo'porce are 
those described by Hagenow, occurring in the Chalk of Maestricht. 
Cymbalopora poeyi, d’Orbigny, sp. (PL CII. fig. 13, a.b.c.). 
Rotalia squamosa, d’Orbigny, 1826, Ann. Sci. Nat., vol. vii. p. 272, No. 8 (name only). 
Rosalina poeyi, Id. 1839, Foram. Cuba, p. 100, pi. iii. figs. 18-20. 
,, squamosa, Id. Ibid. p. 100, pi. iii. figs. 12-14. 
Cymbalopora poeyi, Carpenter, 1862, Introd. Foram., p. 215, pi. xiii. figs. 10-12. 
„ ,, Moebius, 1880, Foram. von Mauritius, p. 97, pi. x. figs. 1-5. 
Amongst the living representatives of the genus, Cymbalopora poeyi is the best 
1 Carpenter alludes to the small dimensions of the recent Cymbaloporoe as compared with the fossil forms, and states 
that “ the diameter of ordinary specimens obtained from deep water at the present time does not exceed j-^th inch ” 
(Introd. Foram., p. 215). This surely is an error ; the typical Cymbalopora poeyi is often j^-th inch, sometimes nearly 
g^th inch in diameter ; and one of the specimens of Cymbalopora tabellceformis now figured measures more than ^bnd 
inch, which is not far short of the dimensions of the Cretaceous species. 
