POLYMORPHINA GIBBA. 255 



PoLTMOEPHiNA (Globulina) GIBBA, Aiidreae, 1884. Abhaudl. geol. Special-Karte 



Elsass-Loth., pp. 209, 233, 

 pi. ix, figs. 10—13. 



— GIBBA, Brady, 1884. ' Challenger' Eeport, p. 561, pi. Isxi, tig. 12. 



— (GrLOBiTLiNA) GIBBA, Basset, 1885. Ann. Soc. Sci. N. Char.-Inf., 



No. 21, p. 161, fig. 63. 



— GIBBA, Sherborn and Chapman, 1886. Journ. Koy. Microsc. Soc, 



ser. 2,vol. vi,p. 755, pl.xvi, 

 fig. 5. 

 _ _ Goes, 1894. K. Svensk. Vet.-Akad. Handl., vol. xxv,No. 9, 



p. 55, pi. is, figs. 522—526, vara. ?). 



— — (forma risTULOSA), Z)e J.wi2CM, 1895. Nat. Sicil., xiv, p. 45. 



— — Chapman, 1896. Journ. R. Micr. Soc, p. 9, pi. ii, figs. 5, 6. 



Charactern. — Shell (typical) subspherical or oval, somewhat produced at the 

 apex, broad and rounded at the base. Chambers few, compact, and overlapping. 

 Sutures marked, not depressed. 



Polyriiorphina gibba is perhaps as definite in typical characters, and as apt for 

 technical description as any member of the group ; still some latitude must be 

 allowed in the terms employed for its diagnosis. D'Orbigny's ' Modele,' No. 63, 

 represents a nearly globular shell, and may be taken as representing the normal 

 form. Our list of synonyms refers to specimens deviating in no striking particular 

 from this standard. 



The shape of the anterior portion of the shell differs considerably in differeut 

 individuals. In some it is acuminate, and the orifice is situate in a mammillate 

 protuberance ; in others it is trunca.te, and the general aperture is flush with the 

 body of the shell. In rare examples the orifice is turned inwards, like that of an 

 Bntosolenian Lagena. 



A compressed variety sometimes occurs bearing a similar relation to P. gibba 

 that P. lactea, var. amygdaloides, does to P. lactea ; and of this d'Orbigny's 

 Globulina sequalis is perhaps the best representative : its synonymy will be found 

 in the Monograph of the genus, op. cit., pp. 216, 217. 



The leading features of the tubulose forms of the Polijmorphinae shown by 

 figs. 70 — 75 in Plate I indicate P. gibba as one of their types. Fig. 71 leans 

 towards P. lactea ; and fig. 74 has a tendency to protrude one of its chambers, 

 like P. problema, but not enough. As for the style of the outgrowths, fig. 70 has 

 them complicated, — that is, both apical and subapical; fig. 71 seems to have had a 

 flat apical mass giving off lateral branches, — acuplacental ; figs. 72, 74, 75 had a 

 very free-growing, branching {racemose), apical outgrowth ; and fig. 73 had an 

 extraneous growth both on the apex and general surface (diffuse) ; fig. 76 is 

 evidently the exposed base of a racemose, or possibly of a placental (cake-like) 

 growth. 



