DlSCO.SCAl'liri'KS, (ioNIATITKS, ETC 221 



Subgenus Macroscaphites, Meek. 

 Shell with iiuier turns merely in contact, or so slightly einhra- 

 ciiig- as to leave a very large, shallow uml)ilicus ; i)eripliery 

 rounded; boclj^ portion much extended from the inner volutions; 



surface costate. S. (iKiAS, Sowl). 



Subgenus Discoscaphites, Meek. 



a. Shell with general outline sul)circular or slightly oval, and 

 generally much compressed ; inner volutions forming a large 

 [)art of the entire bulk, and so deeply embracing as to leave only 

 a small umbilicus ; body portion so short as scarcely to become 

 free at the apertn.re, flattened on the i^eriphery ; surface orna- 

 mented with costit, and provided on each side with from about 

 four to nine rows of tubercles, the outer of which are largest 

 and arranged along each margin of the periphery. Scaphites 

 CoNRADi. Morton. 



b. Shell differing trom the last chiefly in having the volutions 

 so narrow and little embracing as to leave a large, shallow um- 

 bilicus, and the body-volution deviating very little from the 

 regular curve of the others. S. (Ammonites) Cheyennensis, 

 Owen. 



Genus GONIATITES, Dellaan. 



Shell spiral, discoidal ; sutures of septa lol)ed ; siphuncle 

 dorsal. 



About 200 si>ecies. Upper Silurian to Triassic. Europe. 

 G. Henslowi, Sowh. PI. 100. flg. 512. Carb. limestone. Isle 

 of Mo.n. 



Genus CERATITES, DeHaan. 



Shell spiral, discoidal; slightly involuted whorls, generally 

 strongly sculptured ; sutures crenulatel^' lobed, toothed at base. 



Twenty-nine species. Devonian — Chalk. Earojje., India. 

 C. NODOSUS. Brug. PI. 100, fig. 5lG. Muschelkalk. Wurtem- 

 herg. 



Genus BUCHICEEAS, Hyatt. 



Founded on the cretaceous species of Geratifes. which difl'er 

 from the triassic forms in the characteristics of the sutural out- 

 lines : they are not Geratiies at all, but, strictly speaking, Am- 

 monites. They show this in the form of the abdominal cell in 



