GIRTY, THE WEWOKA FORMATION OF OKLAHOMA 147 



shown from the variety sinuosum, though possibly not from M. cornutum 

 itself. The growth lines indicate the presence of a deep hyponomic sinus. 



It may be that these shells represent a young stage of cornutum (though 

 hardly of the variety sinuosum), but they present too important differ- 

 ences (the rapid expansion, greater breadth and differently shaped tuber- 

 cles) to make it safe to assume this relationship without more evidence. 



Horizon and locality : Wewoka formation ; AVewoka quadrangle, Coal- 

 gate quadrangle, Okla. 



Metacoceras cornutum var. multituberculatum var. nov. 



This variety is founded on a crushed specimen which presents the difference 

 from all the others that the tubercles are smaller and more closely arranged. 

 They appear to be somewhat compressed rather than rounded. The umbilical 

 shoulder is subangular without the crest of carinatum, but more rounded than 

 sinuosum. The height between the ventrolateral and umbilical angles is about 

 10 mm. ; the width across the venter (tubercles included), about 15' mm. 



Horizon and locality: Wewoka formation; Coalgate quadrangle, Okla. 



Metacoceras perelegans sp. nov. 



Shell rather small, so far as known not exceeding 31 mm. in diameter. 

 Cross-section of mature whorls hexagonal, transverse ; width about 20 mm. ; 

 height about 12 mm. ; width of lateral zone 7 mm. ; of umbilical zone 6 mm. ; of 

 impressed zone 8 mm. ; of ventral zone, including tubercles, 17 mm. Ventral 

 surface gently convex, flattened or slightly depressed along the center, gently 

 upturned at the edges, owing to the tubercles. Lateral zone nearly flat except 

 for the tubercles, the projection of which gives it a gently concave shape. 

 Umbilical zone nearly flat. The lateral zone slopes gently outward from above 

 and the umbilical zone strongly inward. In the youthful stages, the dimen- 

 sions are increasingly transverse and the shape more nearly elliptical, with an 

 angular periphery a little above the middle and with the usual recurved dorsal 

 zone. This change in shape is effected (when considered in reverse order) by 

 an increased inward slope of the umbilical zone and a corresponding loss of 

 the umbilical shoulder. Both the ventrolateral and the umbilical shoulders, 

 however, are more or less distinguished by an angulation. 



The sculpture of the youthful stages is incompletely known, but the sides of 

 the youngest example seen are marked by fine, even, transverse, rounded 

 stria?, separated by narrow, sharp lirse. Later, the flattened sides are marked 

 by strong, regular plications, the folds being angular and the furrows between 

 relatively broad and rounded. On these are superposed strong, incremental 

 stria?, much less distinct in the furrows than on the crests between them. The 

 pila? thus gradually formed tend to become more prominent at the ends, de- 

 veloping little nodes in which they terminate, the nodes appearing at an early 

 stage and more strongly at the outer than the inner ends. "At maturity the 

 connecting ridges gradually fail of development, leaving the two rows of 



