wanton.] AMALTHEID.E. 169 



"Full diameter of the shell, about 18 cm ; transverse diameter of the 

 aperture, nearly 5 J cm ; long diameter of the same, about 8J cm . 



" Prof. Hyatt writes me, after an examination of the specimen fig- 

 ured on PL xx, that he regards it as a species of his genus Buchiceras, 

 but that, 'it differs from B. syriacum, the type of the genus, in having 

 larger lobes and cells more Ammonite-like.' 



" Position and locality. — Strata of the Cretaceous period ; Glendale, 

 Long valley, Utah." 



The types of the species came from " 4£ miles north of Sherman, and 

 bluffs of Bed river in Fannin and Lamar counties, Texas." I have 

 found a few fragments of it in the Niobrara limestone on Turkey creek, 

 Huerfano park, Colorado. Mr. Walcott collected a number of speci- 

 mens at Upper Kanab, Utah, about 350 feet above the base of the Cre- 

 taceous section. These show a considerable variation and some of 

 them have nodes around the umbilicus and the costae cross the abdo- 

 men, as in Shumard's type. Direct comparison of the Utah fossils 

 with specimens from Texas shows that they are unquestionably iden- 

 tical. Other specimens that are smoother and have a narrower umbil- 

 icus, look exactly like the figure of Placenticeras (perizianum ? var.) 

 liar dense Whiteaves, which occurs in the " Earlier Cretaceous " of Brit- 

 ish Columbia. 



Genus PLACENTICEEAS Meek. 



Placenticeras placenta Dekay (sp.)? 

 PL xxxix, Figs. 1-3. 



Ammonites placenta Dekay, 1828, Ann. N. Y. Lyceum Nat. Hist., vol. II, p. 278, PI. 5, 



Fig. 2, and of various authors. 

 Ammonites (Placenticeras) placenta Meek, 1870, Proc. Am. Pliilos. Soc., vol. xi, p. 



429, and Ann. Rept. U. S. Geol. Sur. Terr, for 1870, p. 297. 

 Placenticeras placenta Meek, 1876, U. S. Geol. Sur. Terr., vol. ix, p. 465. 



Meek's description is as follows : 



"Shell lenticular in form, attaining a large size: umbilicus small; 

 volutions deeply embracing, compressed laterally, with sides converg- 

 ing from near the umbilicus to the periphery, which is very narrowly 

 truncated and flattened or a little concave, with its smooth margins 

 becoming more obtuse with age; aperture narrowly sagittate; surface 

 generally smooth or only showing very obscure traces of curved, trans- 

 versely-elongated prominences on each side, with sometimes a row of 

 very small indistinct nodes around the umbilicus; in young, exfoliated 

 shells also usually showing small, faintly defined, divaricating corruga- 

 tions, directed backward around the outer half of each side. 



" Large examples attain 2 feet or more in their greatest diameter. 

 Young specimens, 3.70 inches in breadth, show a thickness of about 

 0.90 inch, while large individuals are proportionally thicker, and on 

 the periphery become more obtuse. 



