xcviii INFERIOR OOLITE AMMONITES. 



9. Gtraphoceras PLACCIDTJM, 8. Buclcman. Plate VIII, figs. 7, 8; Suppl., Fig. 60 



in text. 



1888. Lioceras concavdm, This Monogr., PI. viii, figs. 7, 8. 

 1902. Gtraphoceras FLACciDUM, Emend. Amm. Nom., p. 4. 



Description. — Concavumbilicate, striiparvicostate, with obscure 

 median undulations. 



Remarks. — Along the median part of the lateral area are ob- 

 scure bulgings after the pattern of those seen in G. undulatuvn. 

 They are drawn too distinctly in the figure. The costae of the 

 outer area are also somewhat obscure. They are drawn rather 

 too distinct, and certainly too numerous in the figure. 

 Fl offfiS« M Localitii and Stratum.— Dorset : Bradford Abbas, Fossil Bed. 



Date of Existence. — Discitse hemera, presumably. 



flaccidum. 



10. GrEAPHOCEEAS ? INCLUSUM, 8. Buclcman. Suppl., Plate XV, figs. 15 — 17. 



Description. — Concavumbilicate, subcostate to striicostate. 



Distinction. — From similar species of the genus, the decidedly smaller 

 umbilicus. 



Localities and Strata. — Dorset: Bradford Abbas, Fossil Bed; Frogden Quarry, 

 Sherborne (' Q. J. Gr. S.,' vol. xlix, p. 500, sect, xv, bed 14. This bed is entered 

 as concavi hemera, but compare fossils with sect, ix, bed 9). 



Date of Existence. — Discitx hemera. 



11. GrEAPHOCEEAS? decorum, S. Buchnan. Plate VIII, figs. 3,4; Suppl., Plate 



XV, fig. 19. 



1888. Lioceras concavum, This Monogr., PL viii, figs. 3, 4, only. 

 1902. Gtraphoceras decorum, Emend. Amm. Nom., p. 3. 



Description. — Subconcavumbilicate, densiparvicostate. 



Distinction. — From G. inclusum, the more open, not truly concave umbilicus ; 

 the more numerous ribs. 



The genus Graphoceras contains many examples of what maybe called concavus- 

 like species — platyleptogyral forms with the little basin-shaped umbilicus, made by 

 the regular superposition of the concave inner margins. There are many more 

 examples of these concavus-\ike or concavumbilicate species, but to describe all 

 these forms adequately would swell this already large Supplement to an inordinate 

 length. Sufficient has been done for the present to show that these concavumbili- 

 cate forms are polygenetic, distinguishable from one another not by shape, but by 

 the curves of the radial lines ; that they are, in fact, the terminals of different grad- 



