1890.] NATURAL SCIENCES OF PHILADELPHIA. 449 



Prodrome de Paleoiitologie, ' has already corrected the error of Nyst 

 and Galeotti, and transferred the species to the Upper Cretaceous 

 horizon (his Senonien), where likewise it is placed by Lycett in his 

 "Monograph of the British Fossil Trigonife."^ 



As regards Ammonites Jlioii, which Nyst and Galeotti compare 

 with ^4. subradiatas (Sovverby) and A. complanatus (Mantell) — the 

 former a Jurassic species, and the latter first described from the Cre- 

 taceous marls of Sussex — there can be no question that the relation- 

 ship is most intimate with the last named. Ammonites subradiatus 

 is a distinctly carinated species, whereas the Mexican form has an 

 evenly rounded dorsum. Again, Ammonites reconditus manifestly 

 represents the type of A. Duvdlianns, D'Orbigny, from the Creta- 

 ceous deposits of France,' and is in no wise a Jurassic form. D'Or- 

 bigny has correctly interpreted the aspect of the Mexican Ammoni- 

 tes by referring them to his Senonian horizon.* 



I can speak with less certainty regarding the two species of sea- 

 urchin which Nyst and Galeotti identify with Cidarites propinquns 

 of Miinster, and C. glandijerus of Goldfuss, since the drawings of 

 the species are not sufficiently precise to permit of absolute determi- 

 nations being made from them. But the form which, from the shape 

 of its spines, is referred to C. glandiferus, appears to be at least as 

 nearly related to the well-known Cretaceous C. clavlgera of Kiinig, 

 whose multiform spines are so largely scattered through the deposits 

 of the Chalk. Cidarites pustulosus is probably a Pseudodiadema} 



The data that have here been given will probably be considered 



1 Vol. II, p. ii40. No. 605. 



2 Palaeontographical Society Reports (Fossil Trigonia;), 1872-79, pp. 181 and 

 229. 



3 D'Orbigny, Paleontologie Francaise, Terrains Cretaces, Atlas, I, pi. 50, 

 figs. 4, 5. 



4 Prodr. de Paleont., II, p. 214. 



* Since the above was written I have received folios 16-20 of vol. XVIII 

 (3rd series) of the Bulletin de la Soc. Geol. de France (1890), containing Cotteau's 

 article : " Notes sur quelques Echinides du terrain Cretace du Mexique." The 

 author reviews the species described by Nyst and Galeotti, and finds their determi- 

 nations erroneous. The form referred to Cidarites propinqwis of Miinster, is an 

 altogether different species ; the so-called Cidarites glandiferus \sz. Psetidocidaris, 

 related to P. clunifera and P. mamniosa ; and Cidarites pustulosus is either Pseu- 

 docidaris or Diplopodia (related to D, \_Pseudodiadenia'\ Afalbosi). Cotteau con- 

 cludes, from the (acies of the echinoid fauna, that the formation which it repre- 

 sents is Cretaceous, and not Jurassic (p. 293). 



30 



