GENUS PATELLINA. 



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umbilical chambers have been so completely altered in fossilization, that I can give no 

 account of their structure; and it is to be regretted that Mr. Carter, whose specimens 

 appear to be in better condition, should have given so imperfect a description and so merely 

 diagrammatic a representation of it. But I can scarcely hesitate in the belief that this 

 columnar chambered structure must essentially correspond with that which we have seen in 

 Tinopoms (f 394), and with which we shall meet again in Orbitoides (^^ 505, 506). It 

 seems most likely that the discoid fossil which has been designated CychUna crclacea by 

 D'Orbigny, is nothing else than a very outspread form of the Orbitolina lenticuhriH of 

 Lamarck, which is probably to be regarded as the fully developed type of our genus Patellina, 

 the recent forms being comparatively feeble. Such a form, agreeing in all essential parti- 

 culars with the foregoing, has been recently described by Mr. Carter (xxiii a). On the 

 other hand, Mr. Carter has met with the same type of structure in very high conical forms ; 

 and in some of these the reticulation of the surface is wanting, and the septa are indistinctly 

 developed. It is not a little curious that in some of these there should be exactly the same 

 disposition of semi-annular imperfectly subdivided chambers interdigitating with each other, 

 as has been described in the recent P. corritgata (^ 404). 



405. Patellina Cooki : External Characters and Internal Structure. — The lossil de- 

 scribed by Mr. Carter (xxiii a) under the new generic name Conulites does not appear to me 

 to differ so essentially from the preceding in general plan of structure as to require being 

 generically separated from it. Like P. lenticularis, it is a more or less depressed cone (Fig. 

 XXXVIII, A, B, c), of which the exterior is formed of a series of chamberlets ( G, 1) arranged in 



Palellina Cooki: — A, B, c, Conical surface, basal surface, and edge view, one half larger than the natural size : — D, Central 

 portion of the spire and chambers magnified, as seen on the surface after the incrustation of the apex has been removed : — e, 

 Vertical section of lialf the fossil, showing, 1, incrustation ; 2, lateral view of chamber-layer ; 3, horizontal layers of chambers ; 

 4, opaque, white columns of condensed shell-substance : — F, Basal surface, showing, 1, ends of the columns of white substance ; 

 2, ends of the columns of chambers :—g. Horizontal section, showing, ], part of the spiral chamber-layer ; 2, truncated ends of 

 opaque white columns ; 3, ditto, of columns of chambers. (After Carter.) 



regular succession, whilst the interior is filled by columnar aggregations of compressed 

 chambers ( g, 2). The arrangement of the chamberlets of the exterior, however, seems from 



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