ART. 17 MOLLUSKS FROM WYOMING EEESIDE AND WEYMOUTH 17 



overgrowth of oysters, but these seem to have grown upon the shell 

 and not upon an internal mold as in the case of some of the speci- 

 mens of Metengonoceras studied by Hyatt. 



The external suture has broad, rather flattened saddles with the 

 first four indented by a tiny marginal lobe. The lobes, on the other 

 hand, are relatively simple, more like those of Albian Metengonoceras 

 than like those of Efengonoceras dumbU. 



The characteristic features of the species in Efengonoceras lie 

 largely in the sutures, for form and ornament are so nearly uniform 

 that they offer little assistsance. E. aspenanuni differs from other 

 American forms in the greater width of the saddles, the small mar- 

 ginals dividing the first four saddles, and in the lesser dissection of 

 the lobes — this is true with respect to species recorded from Texas 

 and several unpublished specimens from the Mowry shale of Wyom- 

 ing. From the French species noted above it may be separated also 

 by the same features of the suture. 



Holotype and paratypes. — Cat. No. 73774, U.S.N.M. 



Family SCHLOENBACHIIDAE 

 Genus ACOMPSOCERAS Hyatt, 1903 



Acompsoceras was proposed by Hyatt *^ to receive the genotype 

 Ammonites hochumensis Schliiter,*^ Amvionites essendiensis 

 Schliiter,*^ and Ammonites renevieri Sharpe.** Pervinquiere *^ in- 

 cluded in the genus, besides the species named. Ammonites sarthensis 

 Gueranger *^ (including A. inconstans Schliiter)*^ and proposed two 

 varieties of A. essendi-ensis., var. nurhilense and var. madjeurense^ 

 which perhaps are better named as independent species. Spath *^ 

 separated from Acompsoceras as Pseud-acompsoceras Schlilter's Am- 

 monites inconstans and Ammonites coupei var. Sharpe *^ (not 

 Brongniart), renaming the latter vectense and making it the geno- 

 type. The conspicuous differences between the genera seem to be in 



^1 Hyatt, Alpheus, U. S. Geol. Survey Mon. 44, p. 111. 



*- Schliiter, Clemens, Cephalopoden der oberen deutschen Kreide : Paloontographica, vol. 

 21, p. 1, pi. 1, figs. 1-4 ; pi. 2, fig. 1, 1871. 



« Idem, p. 3, pi. 1, figs. 5-7 ; pi. 2, fig. 2. 



" Sharpe, Daniel, Description of the fossil remains of Mollusca found in the chalk of 

 England, part 1, Cephalopoda : Paleontographical Soc. Men., p. 44, pi. 20, figs. 2 a, t, C, 

 1855. 



« Pervinqui&re, Leon, fitudes de pal^ontologie tunisienne, pt. 1, C^phalopodes des ter- 

 rains secondaires, pp. 303-308, pi. 17, 1907. 



•*« Gu<5ranger, E., Album palfeontologique du department de la Sarthe (Le Mans), p. 5, 

 pi. 4, fig. 1 ; pi. 8, fig. 2, 1867. 



■" Schliiter, Clemens, Faleontographica, vol. 21, p. 7, pi. 3, figs. 1-5. 



*8 Spath, L. F., On upper Albian Ammonoidea from Portuguese East .\frica, with an 

 appendix on Upper Cretaceous anrmonitcs from Maputoland : Annals Transvaal Mus., vol. 

 11, pt. 3, p. 197, 1925. 



*» Sharpe, Daniel, Paleontographical Soc. Mon., pi. 19, figs. 1 a-c. 



23909—31 2 



