8. S. Buckman — On Jiimssic Ammonites. 359 



Sowerby was not the first to use the name Icevigatus for an Am- 

 monite; and, therefore, d'Orbigny placed the name Davidsoiii instead 

 of IcBvigatus. Oppel, however, says : " As Eeinecke's Icevigatus _ is 

 a poorly-described, ill-defined species, and Lamarck's laivigatus is a 

 synonym of A. Lewesiensis, I make use of Sowerby's name" (Jurat". 

 p. 82). It is wise to follow this example, because there may 

 reasonably be some doubt whether d'Orbigny meant by Davidsoni, 

 which he placed in the Middle Lias, the same species as Sowerby's 

 Icevigatus, which is a well-known Lower Lias form. Further, 

 Dumortier has applied d'Orbigny's name Davidsoni to a species 

 which is not Sowerby's Icevigatus. 



Cymbites Icevigatus is a well-known fossil at Lyme Kegis ; but 

 curiously it found no place in Wright's Monograph. Oppel gives 

 the horizon as just over Am. Bucklandi at Lyme Regis. Hyatt says 

 that it occurs there with obtusus. 



Cymbites Bekardi (Dumortier). 

 1867. Ammonites Berardi, Dumortier, Bassin Rhone ii. pi. 21, figs. 5-7. 



If this be not the young form of a larger Ammonite, then it must 

 be regarded as an evolute development of C. glohosus, which has 

 acquired slight costas, but has not lost its thickness. It looks not 

 unlike a much larger edition of the inner whorls of planicosta; and 

 it may be a species connecting glohosus with planicosta. 



From what Dumortier says, it occurs in the Timieri-zone. 



Cymbites obesus (Eeynes). 



1879. Ammonites ohesiis, Eeynes, Monog. Amm. pi. sxvi. figs. 10 and 11. 

 1887. Agassiceras obesum, Haug, Polymorph. ; N. Jahrbuch fiir Mineral, Bel. u. 

 p. 96. 



This form is the further development— more evolute and showing 

 a faint keel— of a form like the striate glohosus (Hyatt's Icevigatus, 

 pi. viii. fig. 13) ; and it leads to the next species. 



Biicklandi-zone (Keynes). 



Cymbites Davidsoni (Dumortier). 

 1867. Ammonites Davidsoni, Dumortier, Bassin Rhone ii. pi. 21, figs. 1 and 4. 

 1887. Agassiceras Davidsoni, Haug, Polymorphidse ; N. Jahrbuch fiir Mineral, etc., 

 Bd. ii. p. 96. 

 This is a subcarinate form which seems to be merely a compressed 

 development of ohesus occurring on a higher horizon. The com- 

 pression causes a difference in the whorl-shape— in ohesum the 

 whorl is depressed, in this species it is compressed. 

 Turneri-zone (Dumortier, interpreted). 



Cymbites, sp. 

 1885. Ammonites, of. glohosus, Queustedt, Amm. Schwab. Jiu-a, pi. 42, fig. 39 only. 



A somewhat evolute, densisept form which shows a small subcarina. 

 The subcarina, which is a nascent feature in this series, is of interest 

 in connection with Cymbites sternalis (see later). 



Lias ^, Quenstedt. {Margaritatus- or spinatus-zones.) 



