292 Messrs. W. K. Parker and T. R, Jones on the 



over, in this oval shell curiously impress upon the mind its 

 resemblance to a " blown " bird's egg. The minutely sculptured 

 surface also of many eggs is imitated in the Ovulite by minute 

 superficial depressions, leading to tubular perforations ; the 

 shell-wall not being imperforate as in the egg. 



Though usually met with as tiny opake white grains, not 

 unlike seed-pearls, yet occasionally specimens that have escaped 

 molecular change present a clear, smooth, glassy appearance, 

 such as belongs to the hyaline group of Foraminifera. 



This is the largest of the monothalamous Foraminifera, its 

 one cell averaging the bulk of the entire polythalamous shell of 

 Miliola, Rotalite, and many others. The Orbulina universa, 

 which is another single- celled form, never has its individuals 

 larger than third-rate specimens of Ovulites. 



Many small varieties of O. Margaritula retain their beautiful 

 ovoid shape ; but one of the first steps towards degradation is 

 marked by elongation and occasional constriction, giving to the 

 shell a sausage-like appearance. At another step, we have a 

 long straight tube, open at each end (0. elongata, Lamarck); 

 this may be as long as, or longer than, the large oval shells ; 

 and it may be clavate at one or both extremities, like a drum- 

 stick or a "life-preserver." 



The pores in the shell are comparatively large and sparse ; in 

 this it resembles Globigerina ; whilst in Orbulina universa we 

 see, intermixed with these larger pores, a great number of mi- 

 nute tubules. As in large Globigerina from deep water, and in 

 some varieties of Bulimina known as Bolivina, the surface of the 

 shell, in some of the elongate varieties of O. Margaritula, has a 

 delicate honeycomb-like sculpturing, a pore or tubule lying in 

 the hollow centre of each polygonal mesh. 



This monothalamous species, though in some respects compa- 

 rable to the distomous varieties of Lagena (a form related to 

 Polymorphina and Nodosaria), yet has evidently its affinities with 

 the Rotalian group through Globigerina. The enormously 

 elongated cells are not inimical to this view ; for some Rotalice 

 occasionally have wildly-growing, attenuated, and prolonged 

 chambers. 



The Ovulites is of considerable interest in a geological point 

 of view. It appears to have been short-lived as a species. Full- 

 developed in the deposits of Hauteville and Grignon, it breaks in 

 at once in the Eocene period. It lingers as an attenuated form 

 in the Miocene beds of San Domingo. 



We may remark that other Monothalamia, such as Lagena 

 and Orbulina, seem to us to be also of comparatively recent 

 origin; the latter comes to us first in the Miocene, and the 

 former in the Upper Chalk of Maestricht (a deposit which con- 



