Permo-Carboniferous Ammonoids of the Glass Mountains 63 



Uddenites minor n. sp. 

 PI. I, Fig. 24-40 



Shell discoidal, moderately involute, with flat flanks and flattened 

 ventral region, the latter with a median furrow in the adult whorls, 

 and slightly rounded in the younger ones. The furrow is a little nar- 

 rower than each of the flattened parts on either side. The flanks and 

 ventral region form a right angle, but the ventral shoulder is some- 

 what rounded. The cross-section of the adult whorl is nearly rect- 

 angular, if we do not consider that part which embraces the next 

 smaller whorl and the furrow on the ventral portion. The cross-sec- 

 tion of the next smaller whorls without a furrow is rectangular, with 

 a somewhat rounded ventral region ; and the still smaller whorls seem 

 to have an elliptical cross-section. The whorls grow very rapidly in 

 height from' that point where the furrow on the venter begins to de- 

 velop. They even embrace the entire preceding whorl. The umbilicus 

 is moderately narrow. The flank curves down to the umbilical seam 

 in a regular curve. The inner whorls are exceedingly evolute, each one 

 embracing only a small part of the preceding one. The body chamber 

 is unknown. 



The adult whorls do not present any trace of ornamentation. The 

 innermost whorls are also absolutely smooth, but at the part where 

 the Pronorites suture is visible, and the furrow not yet developed, tlie 

 flanks show fairly strong transversal ribs slightly curved with the 

 convexity toward the front, beginning at the umbilicus and disappear- 

 ing before they reach the ventral shoulder. (PI. I, fig. 32.) They 

 are separated by shallow interstices with rounded bottoms, nearly 

 twice as wide as the ribs. At the stage where the furrow begins to 

 develop, the umbilical border shows very fine radial lines of growth, 

 slightly bent backward. 



The septa are not very near together and never touch each other. On 

 the inner whorls they are still farther separated than on the adult 

 ones. The suture is nearly straight. On the inner whorls which have 

 a rounded and flattened venter without a median furrow, the suture 

 is entirely like that of Pronorites and shows the following character 

 (pi. I, fig. 26) : The siphonal lobe appears to be divided into three 

 different parts by the appearance of two secondary saddles on the 

 sides. The middle branch is open below; on each side is a small 



