mSCOSCAPJIITES. GON1ATITKS, ETC, 221 



, 



Subgenus Macroscaphites, Meek. 



Shell with inner turns merely in contact, or so slightly embra- 

 cing as to leave a very large, shallow umbilicus ; periphery 

 rounded ; body portion much extended from the inner volutions ; 

 surface costate. S. UIGAS, Sowb. 



Subgenus Discoscaphites, Meek. 



a. Shell with general outline subcircular or slightly oval, and 

 generally much compressed ; inner volutions forming a large 

 part of the entire bulk, and so deepty embracing as to leave only 

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

 free at the aperture, flattened on the periphery ; surface orna- 

 mented with costa 1 , 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. 



h. Shell differing from the last chiefly in having the volutions 

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

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

 regular curve of the others. S. (AMMONITES) CHEYENNENSIS, 

 Owen. 



Genus GONIATITES, DeHaan. 



Shell spiral, discoidal ; sutures of septa lobed; siphuncle 

 dorsal. 



About '200 species. Upper Silurian to Triassic. Europe. 

 G. HENSLOWI, Sowb. PL 100, fig. 512. Garb, limestone. Me 

 of Man. 



Genus CERATITES, DeHaan. 



Shell spiral, discoidal; slightly involuted whorls, generally 

 strongly sculptured ; sutures crennlately lobed, toothed at base. 



Twenty-nine species. Devonian Chalk. Europe, India. 

 C. NODOSUS, Brug. PL 100, fig. 516. Muschelkalk. Wurtem- 



ber</. 



Genus BUCHICEKAS, Hyatt. 



Founded on the cretaceous species of Ceratites, which differ 

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

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

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



