20 PROCEEDIITGS OF THE N'ATIONAL MUSEUM vol.78 



Bose ^^ reported Metoicoceras as M. aff. whitei Hyatt and M. sp. 

 nov, from beds in Coahiiila, Mexico, which he assigned with some 

 doubt to the upper Cenomanian. He also, as Grossouvre had done, 

 assigned Avimonites geslinianics, particularly as figured by Petra- 

 scheck {PulcheUia gesliniana) , to Metoicoceras. 



Reagan ^^ described Metoicoceras wyomingense from the " Colo- 

 rado series of the Salt Creek region (Big Horn) , Wyoming." It is 

 said to have a broad umbilicus with indefinite shoulders; flattened 

 venter bordered by low, elongated nodes; obscure ribs; no nodes on 

 outer part of flank. The sutures are very ornate for Metoicoceras 

 and have two or at most three lateral lobes instead of four or five. 

 The writers doubt that this species belongs to the genus in question, 

 though it is hazardous to make any final judgment on figures only. 



Moreman ^^ described Metoicoceras irwinl and figured also M. 

 whitei Hyatt, M. swaUowi {=M. whitei variety), and M. gihhosum, 

 Hyatt, all from the Eagle Ford shale of north Texas. 



Metoicoceras may be considered to include ammonites with more 

 or less compressed shells. Umbilicus small, with or without umbili- 

 cal nodes; ribs near umbilicus may be nearly obsolete if there are 

 no umbilical nodes, or strong, rounded if there are. Ribs somewhat 

 flexed to nearly straight, usually forking on the flank; intercalated 

 secondary ribs common. Outer part of flank usually bears distinct 

 ribs and a row of nodes which forms the inner margin of a ventro- 

 lateral facet. Venter bordered by two rows of elongated nodes and 

 in the earlier stages concave or flattened. In late stages the nodes 

 decrease in prominence, the venter becomes rounded, and the ribs 

 pass across as coarse rounded folds. Living chamber usually 

 scaphitoid in large individuals. Suture relatively simple, ceratitic, 

 consisting of three principal lobes, two principal saddles, all more 

 or less clearly bifid, and a few small auxiliaries. 



It may be of interest to characterize briefly the recorded species 

 of Metoicoceras. 



gibhosum. Whorl relatively stout; umbilicus small, one-eighth the 

 diameter; umbilical nodes weak or lacking; ribs weak on inner part 

 of flank, strong and rather coarse on outer part, ending in moderately 

 strong nodes; ventro-lateral facet well defined, marginal nodes 

 relatively high; suture with saddles indented by numerous small 

 marginal lobes. 



swallowi. Whorl not much compressed; umbilical nodes strong, 

 subcorneal; umbilicus relatively wide, one-fourth the diameter; ribs 



°* Bose, Emil, On a new ammonite fauna of the lower Turonlan of Mexico : Texas Univ. 

 Bull. 1856, p. 203, pi. 12, figs. 1-4, 7, 1920. 



"^ Reagan, A. B., Cretacio Mollusca of Pacific Slope : Pan-American Geologist, vol. 41, 

 p. 181, pi. 19, flgs. 1-2, 1924. 



®8 Moreman, W. L., Journ. Paleontology, vol. 1, pp. 92-96, pi. 13, flgs. 3, 4 ; pi. 14, fig. 4 ; 

 pi. 15, figs. 1, 3, 1927. 



