152 University of Texas Bulletin 



the sutures. While our species shows in the inner whorls a rather 

 flattened ventral portion and flattened flanks, V. irregulare has a very- 

 round external side and rounded flanks. Much greater are the dif- 

 ferences in the sutures. In V. irregulare, the second lateral lobe is 

 decidedly asymmetrically bifid and the first auxiliary asymmetrically 

 trifid. This difference is not a question of age only, because those 

 specimens of V. Uddeni which are as large and larger than those of 

 V. irregulare show the same suture as the adults that are smaller, 

 while the interior whorls of this latter species seem to have a suture 

 more or less identical with that of V. Uddeni. The final stage in 

 the adults of both species is therefore entirely different. 



It does not seem that any other species has been described which 

 resembles ours. 



Age: 



This species has beei) found only in the Wolfcamp formation, lowest 

 Permo-Carboniferous. 



Number of specimens examined: 



Nine. The species is rather common at the locality. 



Locality: 



Immediately northwest of Wolf Camp, Glass Mountains. 



Vidrioceras irregulare nov. sp. 

 PI. VII, Fig. 62-73 



Shell rather globose, very involute, with slightly flattened flanks 

 and strongly rounded ventral sides. The umbilicus is very narrow 

 and deep; the umbilical wall is vertical and very broad; the umbilical 

 shoulder is relatively sharp. The cross-section of the whorls is semi- 

 lunar. The numerous whorls grow very slowly in height and are 

 much broader than high. On each exist about three deep transversal 

 constrictions which are strongly curved toward the front. In one 

 of the specimens traces of the ornamentation are preserved on the 

 cast. It consists of broad but very low and somewhat indistinct 

 transversal undulations parallel to the constrictions mentioned above; 

 these undulations or broad and low ribs, are separated bv narrow 

 interstices. The body chamber is unknown. 



