376 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



was not known to Waagen that Meekoceras mushhachamim 

 White possessed the essential characters of Koninckites, 

 for the pubHshed figures of the septa of that species are 

 not exact. But since this is the case, and since M. miish- 

 bachanum was one of the types of Meekoceras, this group 

 of species, characterized by the greater involution, the more 

 rugose shell, and the fourth lateral lobe followed by the 

 auxihary denticulations, is regarded as a subgenus under 

 Meekoceras in the broader sense. There are in the Ameri- 

 can Trias in California and Idaho several undescribed 

 species that will fall under this subgenus. 



Frech^ proposes to drop Koninckites, referring the species 

 described by Waagen under that name to Aspidites. While 

 this is, no doubt, correct for some of the species, it is not 

 correct for the type, nor for species like the type, of which 

 M. mushbachanum is one. 



Meekoceras (Koninckites) mushbachanum White. 



Plate XLI, Figs. 1-3; Plate XLIII, Figs. 1-2. 



1879. Meekoceras mushbachanum, White, Bull. U. S. Geol. Sur. Terr. Vol. 



V, p. 113. 



1880. Meekoceras mushbachanum, White, An. Rept. U. S. Geol. Sur. 



Terr. Vol. XII, Part I, p. 114, pi. xxxii, figs, i, a-d. 

 1902. Prionolobus mushbachanus, Freeh, Lethasa Palccozoica, Bd. II, 

 Lieferung4, p. 631, fig. c. 



Compressed, involute, discoidal, whorl rather deeply embracing, covering 

 nearly three-fifths of the inner volution, and being indented to one-fourth of 

 the height by it. Umbilicus wide, shallow, umbilical shoulders abruptly 

 rounded. Sides more flattened than in M. gracilitatis, gently convex up to 

 the rather narrowly rounded venter. Height of whorl twice its breadth, and 

 nearly one-half of the entire diameter. Width of umbilicus nearly one-fourth 

 of the total diameter of the shell. Greatest breadth of whorl at a point half 

 way between base and venter. 



Surface ornamented with sharp cross striae, slightly curved, and with faint 

 low folds, especially in age. 



Septa ceratitic, saddles all rounded, lobes all serrated. Ventral lobe divided 

 by a broad, shallow, siphonal saddle, the two divisions being serrated by 

 about five denticulations. The first lateral is somewhat deeper and broader; 

 the second lateral about one-half as deep as the first, and smaller, the first 

 auxiliary is small and shallow, provided with several denticulations. Then 



iL,ethffia PaliEOzoica, Bd. II, Lieferung 4, 1902, p. 637. 



