562 
THE VOYAGE OE H.M.S. CHALLENGER. 
Fistulose form (PI. LXXIII, fig. 16). 
“ Polymorpha Corcula Spinosa,” Soldani, 1791, Testaceograpliia, vol. i. pt. 2, p. 114, pi. cxi. fig. Z, Arc. 
Raphanulina humboldtii, Zborzewski, 1834, Nouv. Mem. Soc. Imp. Nat. Moscou, vol. iii. p. 311, 
pi. xxviii. fig. 1 , a. 
Globulina tubulosa, d’Orbigny, 1846, For. Eoss. Vien., p. 228, pi. xiii. figs. 15, 16. 
Polymorphina orbignii (pars), Brady, Parker, and Jones, 1870, Trans. Linn. Soc. Lond., vol. xxvii. 
27, p. 244, pi. xlii. figs. 38, b.f. 
The shell of Polymorphina gibba in its typical condition is nearly spherical, generally 
somewhat produced at the apex and broad and rounded at the base. It usually presents 
three visible segments, which are compactly joined and overlapping ; and the sutures are 
marked by fine lines, neither excavated nor depressed externally. Specimens exhibiting 
more or less lateral compression constitute the Globulina cequalis of d’Orbigny (For. Foss. 
Vien., p. 227, pi. xiii. figs. 11, 12), whilst those which are of oblate contour, that is to 
say, compressed in the direction of the axis, form the Polymorphina gibba, var. orbicularis 
of Karrer. 
The shape of the anterior or oral end of the test differs a good deal in different indi- 
viduals. In some it is acuminate and the orifice is situated on a mammillate protuberance ; 
in others it is truncate, and the general aperture is flush with the body of the shell ; and 
in rare examples the orifice is inverted so as to form an entosolenian tube, as in some of 
the LagencB. 
Polyviorphina gibba cannot be separated from the typical Polymorphina lactea, 
except in a very indefinite manner by comparative characters, and the remarks that have 
been made concerning the distribution of the latter species apply equally to the present 
form. Its occurrence as a fossil has perhaps been even more frequently recorded, 
nevertheless the ascertained geological range is practically the same, namely, from the 
Oolitic period to Post-tertiary and recent times. 
Polymorphina sororia, Reuss (PI. LXXI. figs. 15, 16). 
Polymorphina ( Guttulina ) sororia, Reuss, 1862, Bull. Acad. Roy. Belg., ser. 2, vol. xv. p. 121, 
pi. ii. figs. 25-29. 
,, „ „ Id. 1870, Sitzungsb. d. k. Akad. Wiss. "Wien, vol. lxii. 
p. 487, No. 9. — Schlicht, 1870, Eoram. Pietzpuhl, pi. xxvi. figs. 4-12, 16, 18, &c. 
Fistulose form (PI. LXXIII. fig. 15). 
Globulina horrida, Reuss, 1846, Verstein. bohm. Kreid., pt. ii. p. 110, pi. xliii. fig. 14. 
Aulostomella pediculus, Alth, 1850, Haidinger’s Naturw. Abhandl., vol. iii. p. 264, pi. xiii. 
fig. 17. 
This is another variety scarcely separable from the typical Polymorphina lactea, and 
differing from the latter chiefly in its elongate and subfusiform contour. 
