Weno and Pawpaw Formations 89 



first saddle, lower than first saddle or siphonal lobe. Second saddle still 

 lower, about one and a half times as tall as the first lobe. Second lobe 

 nearly as broad as second saddle, and somewhat lower. Most of third 

 saddle visible externally, lying entirely on steep umbilical wall. Further 

 elements of suture concealed by overlap on next inner volution. All su- 

 tural elements are simple and entire, as in Flickia. 



SCHLOENBACHIA WENOENSIS n. sp. 

 PI. 1, fig. 14 



MEASUREMENTS: (Type individual). 

 Height of volution, 8.0 mm. 

 Width of volution, 4.7 mm. 



HORIZON : Base of Pawpaw formation, clay phase. 



LOCALITY : 723 (type locality) ; 714, both on Sycamore Creek, near 

 Fort Worth, Texas. The species is rather rare; only a few fragments, 

 most of them crushed, have been found. 



The genus Schloenbachia Neumayr, in the restricted sense adopted by 

 de Grossouvre, Pervinquiere and others, includes ammonites with sinuous 

 simple or branched ribs, umbilical and marginal tubercles, and sutures 

 with the first lateral lobe usually trifid. Mortoniceras on the contrary 

 usually has a square cross-section, coarse, almost straight, tuberculate ribs 

 and the suture less dissected than in Schloenbachia, with the first lateral 

 lobe more or less square and bifid. The type species are Mortoniceras 

 texanum (Roemer) and Schloenbachia varians (Mantell). A rather rare 

 pyritic species of the Pawpaw clay is here described on account of its 

 stratigraphic importance. 



DESCRIPTION: Form discoidal, volutions rather flat and broad 

 moderately embracing, outer volution covering about one-third the width 

 of the preceding one, umbilicus therefore wide and open and, on account 

 of the flatness of the volutions, rather shallow; three coils only exposed 

 in the type (fragment), the two inner ones being practically smooth, the 

 outer one decorated with numerous, closely spaced, low, evenly rounded, 

 sigmoidal, branched and simple ribs, most of them having distinct, sharply 

 elevated umbilical tubercles, which are nearly of even height and evenly 

 spaced around the inner margin of the volution ; and near the ventral 

 margin a low overturned, sharp-topped, oblique ridge representing the 

 twin marginal tubercles. On this ridge the more dorsally situated tubercle 

 is represented by a gently curved elevation and the more ventral tubercle 

 is sharper-topped and descends abruptly by a steep ridge and becomes 



