FOEAMINIFEKA OF THE ATLANTIC OCEAN. 63 



spheric, it is often the hirgest chamber of the test, and the number 

 of chambers is often comparatively few. The microspheric form of 

 the same species may start with a very small proloculum and the 

 number of chambers be several times that of the other form. The 

 ornamentation in the group is usually confined to longitudinal costae, 

 or modifications of them, or of spines. In some species there is a 

 definite senescent character in the loss of ornamentation in the later 

 chambers. Other species may show a very definite shape in the last- 

 formed chamber in the adult or in senescent forms, which may be 

 often widely separated from the previously close-set series of 

 chambers. 



Other subgenera have been used, such as Crlandulina, in which 

 there is a tendency for the chambers to reach back and overlap the 

 preceding ones, the last chamber being short and the sutures either 

 close together or indistinct. In Dentalina there is a tendency 

 toward a curved form, with the sutures oblique instead of at right 

 angles to the axis of the test. In the microspheric form of such 

 species there is much greater obliquity of the sutures and usually a 

 greater curvature to that portion of the test. Such species are 

 related to MarginuUna, Vaginulina, and the uncoiled forms of Cris- 

 tellaria. They indicate that perhaps even Nodosaria originated 

 from a coiled ancestor, the coiling being usually lost, except as it 

 shows in the microspheric form. If such is the development of 

 Nodosaria, it is a derivative from a coiled form, similar to Gristel- 

 laria, rather than the coiled forms being derived from straight 

 forms. As both Cristellaria and Nodosaria. are recorded from the 

 Cambrian, it is difficult to say which came first geologically. 



As with Lagena, the species of Nodosaria are here grouped for 

 convenience, usually according to their ornamentation. 



NODOSARIA ROTUNDATA (Renss). 



Olandulina rotundata Reuss, Denkschr. Akad. Wiss. Wlen, vol. 1, 1849, 

 p. 36^, pi. 46, fig. 2. 



Nodosaria (Olandulina) rotundata H. B. Brady, Rep. Voy. Challenger, 

 Zoology, vol. 9, 1884, p. 491, pi. 61, figs. 17-19; Journ. Roy. Micr. Soc, 

 1887, p. 907.— Wright, Ann. Mag. Nat. Hist., vol. 4, ser. 6, 1889, p. 

 449.— Pearcey, Trans. Glasgow Nat. Hist. Soc, vol. 2, 1890, p. 177.— 

 Wright, Proc. Roj\ Irish Acad., ser. 3, vol. 1, 1891, p. 482 ; Irish Nat., 

 vol. 9, No. 3, 1900, p. 54. — Heron-Allen and Earland, Trans. Linn. 

 Soc. London, ser. 2, vol. 11, 1916, p. 255. 



Description. — Test composed of a few chambers, each reaching 

 well back from the preceding, thus forming a compact test, the test 

 broadly rounded, the apertural end slightly extended, with a radiate 

 aperture; sutures distinct; surface smooth. 



Length up to 1.50 mm. 



