128 CARBONIFEROUS AND PERMIAN FORAMINIFERA. 



DENTALINA PERMIANA, Eeuss, 1854. Jaliresb. d. Wetterauer Gesellsch., vol. for 1851 



-1853, p. 73. 

 Richter, 1855. Zeitschr. deutsch. geol. Gesellsch., vol. vii, 



p. 532, pi. xxvi, fig. 27. 

 Geinitz, 1861. Dyas, Heft i, p. 121, pi. xx, fig. 32. 



Schmid, 1867. Neues Jahrbucb. fiir Min., Jahrg. 1867, 



p. 586, pi. vi, figs. 56 64. 



COMMUNIS, Jones and Parker, 1860. Quart. Journ. Geol. Soc., vol. xvi, 



p. 453, pi. xix, figs. 25, 26 (Triassic). 



Brady, 1867. Proc. Somerset. Arch, and Nat. Hist. Soc., 



vol. xiii,p. 107, pi. i, figs. 12, 13 (Liassic). 



Characters. Shell elongate, tapering, more or less curved ; consisting of numerous 

 segments, generally somewhat ventricose. Primordial segment sometimes larger than 

 the second, and either rounded or pointed at its free extremity. The terminal 

 pseudopodial aperture generally excentric, sometimes produced and pouting, but more 

 commonly a simple orifice surrounded by radiating grooves. Septal lines, straight 

 or oblique, generally marked by constrictions. Length yj to inch (1'2 to 4'2 

 mm.). 



For a more extended synonymy of Dentalina communis the reader may be referred to 

 the ' Monograph of the Foraminifera of the Crag,' pp. 57 63. The minute variations 

 observable in individual specimens of this common Foraminifer the foundation of almost 

 innumerable so-called " species " are therein treated at some length, and an endeavour 

 is made to trace the connection that subsists between the members of the various lines 

 of differentiation. It would answer no good purpose to repeat in this place the details 

 of the zoological history of so well-known an organism. The Permian specimens have 

 no single character to distinguish them from those of later geological epochs nor from 

 the living examples dredged in the shallow waters of our coast ; and I can therefore 

 find no reason for giving them another specific name. My friend Professor Rupert 

 Jones, to whose early researches on the Permian microzoa we owe the original description 

 of the ancient examples of this form, coincides in the view that it is better to discontinue 

 the use of a specific name dependent on geological age rather than on zoological 

 characters, and to revert to the earlier d'Orbignian appellation a course which I have 

 not hesitated to adopt. 



Distribution. The geological range of Dentalina communis is much the same as that 

 of Nodosuria radicula. I am not aware that any satisfactory specimens have been found 

 in rocks of the Carboniferous period, but it makes its appearance in the Kupferschiefer or 

 lowest Zechstein of Germany, and occurs also in the Zechstein proper. In England its 

 occurrence is recorded in the Upper Magnesian Limestone only, not in the Middle or 

 Lower division of the Permian system. It is needless after what has been already 

 stated to trace the species through subsequent geological formations. 



