﻿NODOSARIA. 



123 



notwithstanding the great variety, not only in minor characters but in general contour, 

 which exists amongst the specimens included in this comprehensive genus, they form, 

 when arranged, a complete and unbroken series. Prom end to end no link in the chain 

 is wanting, there is no disconnected point at which a sharp line can be drawn to indicate 

 a true specific, much less a true generic boundary. The characters which have been 

 chosen and accepted by a long succession of observers as the basis of an artificial sub- 

 division, though as good as any available under the circumstances, leave the inevitable 

 hosts of " intermediates " unprovided for. It has been said with perfect truth " the 

 group is one in which it is easy enough to establish generic differences when only a few 

 strongly marked types are contrasted, whilst it becomes more and more difficult to 

 maintain these in proportion to the number of individuals compared, until at last the 

 difficulty amounts to an impossibility." 1 To this close connection of a long succession 

 of slight modifications exhibited by individual specimens we owe the prodigious list of 

 needless " specific" names which have been employed for members of the genus ; a 

 category of useless terms which I suspect has no parallel in the domain of systematic 

 zoology. 



Subgenus — Nodosaria, Lamarck. 

 Nautilus, Orthoceras, Orthocera, auctorum. 



Nodosaria, Lamarck, Bef ranee, d'Orbigny, Ehrenberg, Geinitz, Reuss, M'Coy, d'Eichwald, 

 Richter, Parker and Jones, Williamson, Carpenter, Karrer, Brady, Stache, Schmid, $-c. 



Characters. — Shell cylindrical, composed of several segments, arranged in a straight 

 series ; either smooth, or ornamented with ribs, granules, or spines ; septal lines more or 

 less depressed, making constrictions at right angles to the long axis of the shell. 

 Pseudopodial aperture, simple, central, often pouting. 



The artificial nature of the generally accepted subdivision of the Nodosarina could 

 scarcely be more strikingly shown than in a series of Permian specimens. Take an 

 average lot of examples just as they occur in the magnesian limestone debris; — they 

 consist individually of more or less elliptical segments joined together end to end, the 

 segments united by stoloniferous tubes ; no two specimens are alike, they differ in the 

 direction of growth, in the number of chambers, the relative size of succeeding chambers, 

 the degree of convexity of the segments, and in many other quite non-essential particulars 

 yielding characters of not even sub-varietal importance. Systematists begin by assigning 

 the straight individuals to one genus, the bent ones to another. It seems absurd to say so, 

 but it is often exceedingly difficult to determine, under which group of even so elementary 



1 Carpenter, ' Introduction,' p. 159. 



