Nomenclature of the Forarninifera. 113 



In the Tertiaries it is also abundant, and frequently attains a 

 larger size, and puts on a bolder form of growth. In the recent 

 state it is world-wide, localities for large specimens being the 

 Canaries, Mediterranean (especially the Adriatic), Norway coast, 

 and the Abrolhos Bank. Bailey has figured it of a large size 

 from the coasts of the United States. 



17. Nautilus papillosus. Page 82, pi. 14. figs. ac. " Recent : 

 Adriatic/' An elegant variety of Cristellaria Calcar, with a 

 small keel and beaded septal lines. It is thick, and has many 

 chambers. 



18. Nautilus Vortex. Page 33, pi. 2. figs, d-i. " Soldani, 

 Sagg. Oritt. p. 99, pi. 1. fig. 12 ; Testaceogr. vol. i. p. 66, pi. 59. 

 fig. / t" " Fossil : Coroncina." This is a keelless, thick va- 

 riety of Cristellaria Calcar ; it has very narrow and much-curved 

 chambers, the septal lines taking a long, curved sweep to reach 

 the margin. There are many gradual intermediate forms be- 

 tween this and the type. It is not unfrequent in clays of the 

 Mediterranean, at about the depth of 90 fathoms ; and it occurs 

 fossil in the Tertiary clays of Tuscany, Vienna, and Malaga. 



D'Orbigny has given two figures of this variety : that of his 

 Robulina orbicularis, Annales Sc. Nat. vol. vii. p. 288, No. 2. 

 pi. 6. figs. 8, 9 ; and that of his R. Imperatoria, For. Foss. Vien. 

 p. 104, pi. 5. figs. 5, 6. The former differs from Cristellaria 

 Vortex in having a slight keel, in not being quite so thick, 

 and in being somewhat umbonate. R. Imperatoria, having the 

 same amount of keel as R. orbicularis, is less gibbous, but more 

 distinctly umbonate than the latter. These slight and almost 

 insensible degrees of modification render the three shells here 

 referred to notable examples of the gradual passage so often 

 recognizable between varietal forms of species. The roundness 

 and plumpness of Cristellaria Vortex is modified to the lenticular 

 and comparatively lean C. Imperatoria, having markedly con- 

 tracted chambers (the narrowest of any Cristellaria) and a pout- 

 ing aperture, which is lost in the greater fulness of the chambers 

 of C. Vortex and C. orbicularis. Full-sized and entire-keeled 

 specimens of C. Vortex, supplying still further intermedia, are 

 figured by Soldani. 



19. Nautilus costatus. Page 47, pi. 4. figs, g, h. " Recent : 

 Mediterranean, Coast of Africa." A Cristellaria, more or less 

 keeled ; the keel is somewhat toothed ; the septal lines are raised 

 or limbate, a character which, however, is absent in D'Orbigny's 

 figured specimen of a similar variety from the Tertiary beds of 

 Vienna (Robulina Ariminensis, For. Foss. Vien. pi. 4. figs. 8, 9) ; 

 the chamber-walls are regularly marked with numerous ribs at 

 right angles to the septal lines. In this variety of C. Calcar 

 (which is not of common occurrence, but sometimes met with in 



