150 ANNALS NEW YORK ACADEMY OF SCIENCES 



Sculpture consisting of angular pilae or plications at the sides with relatively 

 broad, rounded interspaces. The pilae are short and divide irregularly into 

 three or four branches of inferior size and prominence. Similar small plica- 

 tions are developed simultaneously in the sulci between the pilae, all of whicb 

 become crowded and finer, so that the venter is crossed by regularly arranged, 

 moderately coarse and strong striae which form a rather broad, deep sinus as 

 they cross to the other side. 



The suture is rather simple. The siphonal saddle is small and indented on 

 top. The remaining lobes and saddles are rounded. The first lateral saddle 

 is rather broad and symmetrical ; the second, still broader and very unsym- 

 metrical, the outer side being straighter and more extended than the inner. 

 The two lobes are symmetrical. The first is very small, narrower than the 

 siphonal saddle. The second is fully twice as large as the first and somewhat 

 more spreading. 



This species resembles the few Gastriocerata described from the Carbon- 

 iferous of America which have plicated sides, but the plications in this 

 case are finer and branching in a rather unusual manner. The suture is 

 also distinctive in that the lobes are rounded instead of angular. In some 

 respects the characters shown by this species suggest that it is an imma- 

 ture stage, but some fifteen specimens have been examined, all of which 

 are of small and more or less uniform size. 



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

 gate quadrangle, Okla. 



Gastrioceras hyattianum sp. nov. 



Shell subspherical with relatively wide umbilici when young; compressed 

 globose with relatively narrow umbilici when mature; attaining a rather 

 large size, the largest example having a diameter in the plane of revolution of 

 65 mm. and being about .37 mm. thick at the widest part of the final volution. 

 Umbilical shoulder angular and more or less carinated at all stages, except 

 perhaps when very immature. Cross-section broadly lunate in the young and 

 narrowly lunate in the mature condition. In the latter, the curve of the venter 

 and sides I which are not differentiated) is parabolic, gradually expanding 

 toward the umbilicus and much more strongly curved above than at the sides. 

 In this condition the whorls are deeply embracing. Specimens of nearly the 

 same size seem to vary considerably in thickness, some being more discoidal, 

 others more globose. The chamber of habitation is long, one volution or pos- 

 sibly more. 



The surface when very young is probably cancellated with fine transverse 

 lira 3 and fine revolving ones. In an early mature condition, the strength of 

 the liration seems to have dimin'.shed considerably. The transverse lira? are 

 finer but persistent, while the revolving lira? become restricted to the umbilical 

 surface and the sides of the ventrolateral surface, the major portion of the 

 venter showing only transverse markings. These have a more or less sinuous 

 course with a gentle saddle in the center and obscure lobes toward the sides^ 



