UPPER CRETACEOUS: DOUBTFUL FORMS 135 



Stagodoti Marsh 

 1889. Stagodon, Marsh, Amer. Jour. Set. (3) XXXVIII, 178. 



Species. — Stagodon vitor, Marsh 1889, loc. cit., genotype. Type: a single pre- 

 molar from the Lance of Niobrara County, Wyoming. 



Stagodon tumidus, Marsh 1889, loc. cit. Type: a single premolar from the Lance 

 of Niobrara County, Wyoming. 



Stagodon valtdus, Marsh 1892, Amer. Jour. Set. (3) XLI II, 256. Type: anterior 

 part of right lower jaw with crown of P,-). 



Description. — "[In S. tiitor] the striking character of all the molar teeth se- 

 cured is the resemblance of their crowns to a drop of viscous fluid. ..." "[S. valtdus] 

 shows alveoles for three incisors closely crowded together, the first, or inner one, being 

 much the largest. A very stout canine . . . was present, and behind it, in close contact, 

 follow two premolars, the second being much the larger. These are both much worn, 

 but the surface of the crowns preserved is coarsely striate or rugose. ..." 



Stagodon includes only premolars of Didelphodontinae, and is undoubtedly 

 synonymous in whole or in part with Didelfhodon, Thlaeodon, or Ectoconodon. Com- 

 plete cheek series of these and of any other genera which may occur would be necessary 

 to elucidate the true synonymy, and in any event it would seem unwise and unneces- 

 sary to replace any of the names based on molars by Stagodon, based on material which 

 is generically uncharacteristic. 



Dryolestes tenax Marsh 1 889 

 1889. D. tenax. Marsh, Amer. Jour. Sci. (3) XXXVIII, 87. 



Xype. — Y.P.M. No. 10698, lower jaw without teeth. 

 Horizon and Locality. — Lance, Niobrara County, Wyoming. 



The type jaw is a small didelphid and has nothing to do with the Jurassic genus 

 Dryolestes. Otherwise it is indeterminate and the name a nomen nudum. 



Platacodon Marsh 

 1889. Platacodon, Marsh, Amer. Jour. Sci. (3) XXXVIII, 178. 



Species.—/', nanus, Marsh 1889, loc. cit., genotype. Three teeth from the Lance 

 of Niobrara County, Wyoming. 



Hatcher (1900) has adduced evidence that these are fish teeth and not mamma- 

 lian, a possibility which Marsh recognized. 



Synconodon Oshovn 1898 

 1898. Synconodon, Osborn, Bui. Amer. Mus. Nat. Hist., X, 171. 



Species.— 5". sexcusfis, Osborn 1898, loc. cit., genotj'pe. Syntypes: A. M. Nos. 

 2218, 2220, isolated upper and lower molars, from the Lance of Niobrara County, 

 Wyoming. 



