GENUS TINOPORUS. 223 



387. Varieties. — The highly developed type which is now being described, is subject to 

 considerable modification in feebler forms. One of these, the C. culcar of D'Orbigny (xcii), is 

 remarkable for the radiating prolongations of the chambers themselves (Plate XIII, fig. 21), 

 every one of which is ensheathed by a layer of exogenous substance that extends itself to form 

 the points of the ray. 



388. AJJinities — Although I consider the difference of aperture, with the extraordinary 

 development of the supplemental skeleton and its canal-system, as sufficient, when taken 

 together, to give to Calcarina a title to distinct generic rank, yet there can be no question of 

 its extremely close relationship to liotalia. The arrangement of the chambers is in all 

 essential particulars the same as that which is characteristic of that genus ; and the 

 subdivision of the fissured aperture of the Itofalina into a row of pores is no greater a 

 difference than that which we shall find to exist between the " nonionine" and the typical Polj/- 

 sfomella, being moreover absent in some feeble CalcarincB, whilst it presents itself in a variety 

 of the true Eofalia. In certain forms of Ttotalia we have had to notice a considerable deve- 

 lopment of the supplemental skeleton, which sometimes extends itself into i-adiating out- 

 growths ; and where this exogenous deposit is formed in largest amount, we find the canal- 

 system most complete and symmetrical. Thus the characters which differentiate Calcarina 

 from Rolaliu are altogether gradational. 



389. Geoc/raphical and Geological Distribution. — The generic type we have now been consi- 

 dering appears to be pretty widely diffused through the tropical and warmer temperate seas, 

 but to be limited to these ; the Mediterranean and Adriatic being its extreme northern limit. 

 Although bodies resembling Calcarina in outward form are occasionally, though rarely, found 

 in the White Chalk, yet it is not certain whether they belong to this or to the succeeding genus. 

 The Maestricht beds, however, are crowded with CalcarincB {Siderolince, Lam.), which attain 

 an extraordinary development, their size much surpassing that of the largest specimens now 

 living in tropical seas. This type is common in the Grignon Tertiaries, also in the Miocene 

 of North America, and in European Pliocene deposits ; and I also have examples of it from 

 deposits in Madagascar and Bourbon, the age of which is uncertain. 



Genus XIX.— Tinoporus (Plate XV). 



390. History. — For reasons which will be presently explained, I think it well to revive a 

 generic designation originally instituted by De Montfort in 1808, although, like a large pro- 

 portion of his new designations, it has been rejected as uncalled-for by subsequent systema- 

 tists. In his ' Conchyliologie Systematique' (tom. i, p. 147), he described and figured under 

 the name of Tinoporus baculatus a small polythalamous body, which he seems to have distin- 

 guished from the other varieties of Nautilus {Calcarina) Sjjenf/leri figured by MM. Fichtel and 

 Moll, partly by the fewness of its spines, and partly by the difference of its structure as 

 displayed in vertical section. And although his figure and description are alike 

 inaccurate (the former, as pointed out by Messrs. Parker and Rupert Jones, lxxvii, 

 having been partly drawn from specimens of Calcarina), yet I can scarcely doubt that 



