CRISTELLARIA CULTRATA. 239 



General Characters. — See also Part I, p. 72. Test planospiral in part or 

 entirely; discoidal, complanate, lenticular (biconvex), crozier-shaped or ensiform ; 

 chambers subtriangular, sickle-shaped or of other hook-like form, mostly compact ; 

 smooth, limbate, granulose, or longitudinally costulate. 



The smooth lenticular Gristellaria without a keel is G. rotulata (Lamarck) ; 

 with a keel G. cultrata (Montfort) ; with broad, dentate keel, G. calcar (Linne) ; 

 and when much compressed, broadly keeled, and ornamented, it is G. cassis 

 (Fichtel and Moll). Parker and Jones adopted G. calcar as the best central and 

 representative type of Gristellaria. G. cultrata and rotulata are inferior to it in 

 point of development, whilst G. cassis surpasses it in the augmentation and diversity 

 of ornamental and marginal growths. 



As these forms are very variable in the several features and graduate one into 

 the other, their separation into quasi-species is quite of an artificial character ; and 

 it is often difficult to determine to which group some individuals should be allocated. 

 In the following synonymy only the best marked figured specimens have been noted. 



G. cultrata, being present in the Crag, is here described. 



1. Cristellaeia culteata (Montfort), 1808. Plate I, figs. 24, 25. 

 Part I, 1866, Append. I and II, Tables, No. 47. 



Cornu Hammonis, Plancus, 1739. De Conchis minus notis, «fec., p. 12, pi. i, figs. 3, 



G, H, i;i edit; 2, 1760, p. 120, pi. i, figs, xii, 

 s, T, V, and xiii z Z. 



Corn-ammone, Oinanni, 1757. Opere postum., vol. ii ; Teat. Adriat., p. 20, pi. xiv, 



fig. 113.2 



Nautilus calcae, Linne, 1758. Syst. Nat., 10th edit., p. 709 ; and 12th edit., 



1767, p. 1162, No. 272. [This includes 

 Cristellaria cassis, calcar, and cultrata.'\ 



Nautili Circumalati seu marginati grandiusculi, Soldani, 1780. Saggio Oritt., p. 97, 



pi. i, fig. G. 



^ Gr. Bianchi states, at p. 13, that the majority of these have a broad pellucid, margin around the 

 shell ; therefore they are the same as G. cultrata. In the 1760 edition there are added to the plate 

 figs, xii, s, T, V, and xiii, Z z, which appear to be true cultrata. The fig. 3 quoted above appears to 

 belong to the minority, namely, those without the broad pellucid margin, and is therefore rotulata ; 

 and this notwithstanding the remark at p. 13, that the artist has not (but might have) shown the 

 marginal flange. See also Fornasiui, 'Boll. Soc. Geol. Ital.,' vol. vi, 1887, p. 38. 



2 In these posthumous papers of Count Giuseppe Giuanni, of Kavenna, fig. 113 is evidently a 

 bad drawing of Cristellaria cultrata ; and, as is the case also with figs. 112 and 114, it lias an 

 irrelevant description taken wrongly from Plancus. Fig. Ill is one face, and fig. 112 probably the 

 other of Rotalia Beccarii ; and fig. 114 is possibly a poor Crist, cassis. 



