Geol.— Vol. I.] SMITH— COMPARATIVE STRATIGRAPHY. 369 



M. gracilitatis as the type, and placed all other kindred 

 but dissimilar forms under different genera, thus restricting 

 the genus to narrower limits than was intended by Hyatt. 

 The evolute forms without auxiliaries, such as M. aplana- 

 tum, were placed under a new genus, Gyronites, which 

 would include most of the forms assigned by Mojsisovics to 

 Xenodiscus. Species with a fourth lateral lobe followed by 

 a series of auxiliary denticulations, such as M. mushbach- 

 anmn, were assigned to the new genus, Koninckites 

 Waagen. Forms in which the auxiliary series had no 

 individualized lobe, but consisted of merely a few denticu- 

 lations were assigned to Kingites Waagen. 



C. Diener^ regards Kingites and Kotmickites merely as 

 subgenera of Meekoceras, in which conclusion the writer 

 agrees with him. In a later paper Diener^ includes also 

 Aspidites Waagen and Beyrichites Waagen under Meeko- 

 ceras. But these two types are different from any included 

 by Hyatt under the original description, and it seems best 

 to let them stand as independent genera. 



As thus defined, Meekoceras in the broader sense would 

 include all species similar to the three typical forms, and 

 the species nearest to M. gracilitatis White would be 

 classed under Meekoceras in the limited sense. 



Since M. aflanatiim White has all the characters of 

 Gyronites Waagen, all species similar to it are placed in it 

 as a subgenus under Meekoceras. 



Examination of the types in the United States National 

 Museum has shown that Meekoceras mtishbachanum White 

 has all the characters assigned by Waagen to Koninckites, 

 and since this species was one of the types of Meekoceras, 

 all species similar to it are classed in the subgenus Kon- 

 inckites. 



Aspidites and Beyrichites are regarded by the writer as 

 independent genera. The systematic position of Prionolo- 

 bus Waagen is somewhat doubtful, but it should probably 

 be placed as a subgenus under Meekoceras. 



1 See Bibliog. 5— p. 46. 

 'See Bibliog. 3— p. 126. 



