ART. 17 MOLLUSKS FROM WYOMING REESIDE AND WEYMOUTH 23 



as Texan specimens in full agreement with it are abundant. Brief 

 characterizations of the two forms included under lohitei are given 

 above. 



Eight more or less fragmentary molds of the exterior of a species 

 of Metoicoceras are here referred to M. whitei Hyatt, s. s. The 

 sutures are entirely unknown and the form must be in part inferred 

 because of accidental compression during fossilization. Neverthe- 

 less the ornamentation is sufficiently in agreement to warrant the 

 assignment. The ventrolateral facet is not well shown on some of 

 the specimens, but this feature is probably a result of the manner 

 of preservation. 



Metoicoceras whitei (in the broad sense) is known at various local- 

 ities in the Mowry shale of central and eastern Wyoming, the Green- 

 horn limestone of the Great Plains region and Black Hills, the 

 Mosby sandstone member of the Warm Creek shale of Wyoming, the 

 basal part of the Colorado group of Utah and New Mexico, usually 

 in all these formations in association with Inoc&fanius Idbiatus 

 Schlotheim and unquestionably of lower Turonian age. 



Plesioty pes. —Csii. Nos. 737T6, 73777, U.S.N.M. 



METOICOCERAS species 



Plate 2, Figure 1 



A single mold of the exterior of the shell of a small Metoicoceras 

 differs from accompanying M. whitei in its feeble sculpture and in 

 the development of elongated riblike prominences near the middle 

 of the flank of the outer whorl. This feature does not accord with 

 any described species of Metoicoceras^ but the writers do not venture 

 to assign a name to the form without more adequate material. 



Cat. No. 73778, U.S.N.M. 



EXPLANATION OF PLATES 



Except for plate 2, Figure l,and plate 4, Figures 3, 4, and 7, all specimens shown 

 are from the Aspen shale, 80 feet below the top, in the NW.M of sec. 32, T. 21 N., 

 R. 115 W., Lincoln County, Wyo. The excepted specimens are from the Aspen 

 shale, 350 feet below the top, in sec. 17, T. 16 N., R. 117 W., Uinta County, Wyo. 

 All figures are natural size except where enlargement is indicated. 



Plate 1 



Page 



Figure 1. Periplomya? aspenana Reeside and Weymouth, new species, 



the holotype, a natural cast of the exterior, U.S.N.M. Cat. No. 73765__ 7 



Figures 2, 3. Anomia species, two plaster casts from natural molds of the 



exterior. U.S.N.M. Cat. No. 73764 7 



Figure 4. Tellina? species, view (X 2) of a natural mold of the interior 



retaining part of the shell. U.S.N.M. Cat. No. 73770 10 



Figure 5. Pterin (Oxytoma) species, view (X 5) of a wax squeeze from a 



natural mold of the exterior. U.S.N.M. Cat. No. 73763 6 



Figure 6. Tancredia? lincolniana Reeside and Weymouth, new species, 



plaster cast from the holotype, a natural mold of the exterior. U.S.N.M. 



Cat. No. 73767 8 



