8o BUI^LETIN 31 80 



In differentiating this species hoiwalticostata, it will be noticed 

 that rotunda has in general a more nearly circular outline ; there 

 is less of a post-umbonal flattening ; there are but two or three 

 rather conspicuous costse below the ligamental margin, whereas in 

 alticostata there are four and the fourth is oftentimes strongest of 

 all ; the ornamentation or serration is much finer than in alticos- 

 tata and the terracing of the ribs is shown, if at all, mediall}' and 

 not most strongly towards the anterio-submargin as in alticostata. 

 The hinge teeth are comparatively thick and robust in rotunda. 

 However, there • are a few specimens one finds in sorting over 

 hundreds of rotunda that show a tendenc}^ toward a quadrate 

 form and have the costal serration approaching that of alticostata. 

 But the strong fourth rib below the ligamental margin is lacking, 

 likewise the strong terracing anteriorly. 



Types. — Probably No. 5267, of the Phila. Acad. Coll. was 

 the specimen from which Lea's figure w^as drawn ; features used 

 in the description of the species were doubtless derived from Nos. 

 5268-70. T}'pes of the va.x\Qt\es fujigina Q.nd funiculus are in the 

 Paleont. Museum at Cornell. 



Horizon. — Claibornian and Jacksonian stages. 



Localities. — Texas : Smithville, Bastrop Co. ; Burleson Shell 

 Bluff, Brazas Kiver ; 3 miles N. F. of Alto, Cherokee Co. ; Hur- 

 ricane Ba3'ou, Marsters and Hodge headright, Houston Co. 

 Miss. : Wautubbee. Alabama : Claiborne "sand", Claiborne. 



Venericardia rotunda, var. flabellum, n. var. PI. 29. Fig. 8. 



General appearance as figured ; beaks more pointed than in 

 rotu?ida, s. s. ; ribs about 21, ornamented by broad, blunt nod- 

 ules and rarely showing in adult stage lateral terracing. 



This is a very abundant type at Smithville, Tex. 



Venericardia (rotunda) varying toward trapaquara, PI. 29. Figs. 6, 7. 



A small form with inflated umbonal region, a tendency to- 

 ward a squarish outline and with ribs showing about as much 

 lateral terracing as rotunda and with crenulation intermediate in 

 character .h&tw&^n fimgina 2ii\d funiculus ; an immediate descend- 



