of Arenaceous Foraminifera. 205 



Prof. Williamson and the late Prof. Max Schultze, in con- 

 sidering Lituola canariensis = Nonioni7ia Jeffreysn, not only as 

 being perforate on the surface, but as being only an arenaceous 

 form of Nonionina (now with Operculina very properly in- 

 cluded in the family Nummulitida by Dr. Carpenter). By 

 which I mean that the Arenaceous Foraminifera should not 

 be separated from the tests of which they are but the are- 

 naceous forms respectively. I do not mean to state that N, 

 Jeffrey sit is typically the same in structure as the " vitreous " 

 Nonionina J but that it is so as far as the heterogeneous ma- 

 terial of which it is composed will permit. (" Hyaline or 

 vitreous," Introd. p. 44, are bad terms for the earthy Num- 

 mulitic character, although good for the test, generally minute, 

 which is as transparent as glass.) 



Indeed it would appear impossible to view the transverse 

 section of Valvulina (fig. 23), whose test is partly composed 

 of vitreous and partly of arenaceous structure (fig. 24, ^, c) — 

 that is, the former secreted by and the latter brought to 

 the animal (by what? Not its " pseudopodia," but by the 

 sarcodic filaments of the surface) — without assuming that the 

 tubulation of the vitreous (fig. 24, h) is continued throughout 

 the arenaceous layer (fig. 24, c), even if it were not distinctly 

 visible in most species of this Foraminifer. But Dr. Car- 

 penter, to get over this difficulty, would "assign to it [Valvu^ 

 Unci] an independent position as the connecting link between the 

 two " (' Introd.' p. 146) — that is, between the " Imperforate " 

 or Arenaceous and the Vitreous or Perforate Foraminifera. 

 To me this "connecting link" is an indication that the " two" 

 should never have been separated in classification. 



Scratch off the outer portion of a Valvulina (fig. 24, c), and 

 a Textularian test makes its appearance (fig. .24, h) ; that 

 is, a Valvulina is at first a Textularia and then a Valvulina^ 

 Scratch off even the thinnest portion of the surface of Lituola 

 canariensis, and it directly, for reasons before mentioned, pre- 

 sents crevices or pores like those of Valvulina both in size and 

 shape (fig. 27, 6) ; or break open the test itself, and the in- 

 tercameral holes of the septa (fig. 28, a), together with the tu- 

 bulation of the walls (fig. 28, bbb), are, mutatis mutandis, the 

 same as in Nonionina among the Nummulites. That is, the 

 homogeneous composition and definite form of the cavities in 

 the latter are exchanged for the heterogeneous composition and 

 consequently ill-defined form of the cavities in the former (fig. 

 28, a, b)j where most of the sand-grains composing the test are 

 from ten to twenty diameters larger than that of the tube itself 

 in Operculinaj to say nothing of the pore in its centre. 



In short, where the straight tubulation ends in Valvulina 



