ART. 17 MOLLUSKS FROM WYOMING REESIDE AND WEYMOUTH 19 



umbilical nodes, proportions of the suture, and stouter sutural ele- 

 ments, though the degree of dissection is nearly the same; from 

 A. essendiense (Schl titer) also by its more numerous ribs and by its 

 less dissected suture; from A. renevieri (Sharpe) by its more numer- 

 ous ribs, shorter siphonal lobe, and stouter sutural elements; from 

 A. mrhileiise Pervinquiere by its less rounded sutural elements and 

 lack of umbilical nodes; from A. tnadjeurense Pervinquiere by its 

 coarser ribs, earlier loss of the ribs, and less rounded sutural 

 elements. 



This occurrence of Acoi7ipsoceras does not accord with the current 

 assignment of the genus solely to the Cenomanian. The strati- 

 graphic relations and the associated fossils argue for the lower 

 Turonian age of the present fauna. It is the first record, so far as 

 the writers are aware, of the genus in the United States. 



H olotype. —Cvii. No. 73775, U.S.N.M. 



Family METOICOCERATIDAE Hyatt, 1903 



Genus METOICOCERAS Hyatt, 1903 



Metoicoceras was instituted by Hyatt ^^ in 1903 with Ammonites 

 swaUowi Shumard ^^ as the first species described under the genus and 

 therefore usually considered the genotype. In addition Hyatt de- 

 scribed as new M. gibhosuin, M. whitei, and M. acceleratum. Hyatt 

 also figured arid named M. kanabeme without description. The geno- 

 type species was recorded from the Turonian Eagle Ford shale of 

 Texas, gibhosum from Texas, whitei from Texas and Utah, accelera- 

 tum from Texas, and kanahense from Utah. 



Leriche^^ described Metoicoceras pontieri from the base of the 

 Turonian in the north of France, and Grossouvre =^ described, as 

 species of Mammites, Metoicoceras pervinquierl, M. gourdoni, M. 

 petraschecki, M. hureaul, M. dumasi, and with these referred to 

 Mammites (Metoicoceras) D'Orbigny's Ammonites geslinianus.^'^ 

 These are assigned to the lower Turonian of western France. 

 Spath ^^ later assigned the horizon of M. pontieri to the top of the 

 Cenomanian. 



°o Hyatt, Alpheus, U. S. Geol. Survey, Mon. 44, p. 116. 



81 Shumard, B. F., Descriptions of new Cretaceous fossils from Texas : Acad. Sci. St. 

 Louis Trans., vol. 1, pp. 591-592, 1859. 



83 Leriche, Maurice, Sur la presence du genre Metoicoceras Hyatt dans la Craie du Nord 

 de la France et sur une esp&ce nouvelle de ce genre (Metoicoci:ras poniieri) : Soc. G^ol. 

 Nord (France) Annales, \ol. 34, pp. 121-124, pi. 2, text flgs. 1-3, 1905. 



83 De Grossouvre, Albert, Le Cr6tac6 de la Loire- Infgrieure et de la Vendue: Soc. sci. 

 nat. Guest France Bull., ser. 3, vol. 2, pp. 11-25, pis. 1-2, text figs. 1-2, 1912. 



^* D'Orbigny, Alcid, Pal(5ontologie frangaise, ser. 1, Terrain crt'tacg, vol. 1, p. 325,. 

 p!. 97, figs. 1-2, 1840 ; Prodrome de paK'Ontologie, vol. 2, p. 146. 1850. 



83 Spath, L. F., On new ammonites from the English chalk : Geol. Mag., vol. 63, p. SO, 

 1926. 



