28 BULLETIN" 11, UNITED STATES NATIONAL MUSEUM. 



the following chambers gradually decreasing in relative length, more 

 or less loose coiled, the intermediate area filled in with a shelly plate; 

 aperture at the end of the chamber, rounded, without Up or teeth. 



The genus Opthalmidium is very evidently an advance from 

 Cornuspira toward a condition seen in the genus Spiroloculina. The 

 relative length of the second chamber shows a decidedly primitive 

 character and the succeeding relative shortening of the chambers is 

 also decidedly primitive, characters which in the development of 

 Spiroloculina are greatly reduced by acceleration of development. 



Opthalmidium is rather rare in recent oceans, but in the Lias 

 especially seems to have been much more abundant and characterized 

 by more species than at present. 



OPTHALMIDIUM INCONSTANS H. B. Brady. 



Plate 3, figs. 1-4. 



Hauerina inconstans H. B. Brady, Quart. Journ. Micr. Sci., vol. 19, 1879, p. 54. 

 Opthalmidium inconstans H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 



1884, p. 189, pi. 12, figs. 5, 7, 8.— H. B. Brady, Parker, and Jones, Trans. 



Zool. Soc., vol. 12, 1888, p. 216, pi. 40, figs. 12, 13.— Egger, Abhandl. bay. 



Akad. Wiss. Munchen, CI. n, vol. 18, 1893, p. 244, pi. 3, figs. 6, 49— Millett, 



Journ. Roy. Micr. Soc, 1898, p. 608. — Chapman, Journ. Linn. Soc. Zoology, 



vol. 30, 1910, p. 398. 



Description. — Test planospiral, much compressed, chambers con- 

 sisting of a globular proloculum, followed by a Gornuspira-like coiled 

 second chamber, making two or more volutions, this in turn followed 

 by chambers progressively relatively shorter in length until the adult 

 condition is reached, where chambers are half a volution in length 

 or less, chambers nearly circular in transverse section with a thin 

 wide flange on the peripheral border, chambers often slightly less coiled 

 toward the apertural end, leaving a space filled by a thin plate of 

 shelly material; aperture circular without lip or teeth. 



Diameter, about 1.5 mm. in the largest specimens. 



Distribution. — Brady records in his generalized statement that he 

 had this species from the North Pacific, but gives no definite stations. 



The only material I have had is from Nero station, 1466, in 234 

 fathoms off Guam. 



OPTHALMIDIUM TUMIDULUM H. B. Brady. 



Plate 3, fig. 5. 



Opthalmidium tumidulum H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 

 1884, p. 189, pi. 12, fig. 6. 



Description. — "Test complanate, commencing growth as a rounded 

 tube coiled upon a somewhat inflated primordial chamber in a 

 planospiral manner; the earlier convolutions nonseptate and cornu- 

 spira-like, the subsequent ones constricted at intervals and eventually 

 more or less regularly Spiroloculine; peripheral edge rounded. Aper- 



