150 Trans. Acad. Sci. of St. Louis. 



The dimensions of an average specimen are, length 4^- 

 mm. ; breadth 6 mm. ; and convexity 1 mm. 



Remarks. This little species occurs in vast numbers in 

 the thin Chonetes bed of the Burlington section. In general 

 outline and in size it resembles C. geniculates White, from 

 the Louisiana limestone, but it differs conspicuously from 

 the latter in its much finer and far more numerous radiating 

 striae. It also resembles C . scitulus Hall from the middle 

 and upper Devonian faunas of New York, but is usually 

 smaller and always has much finer radiating striae. White 

 seems to have identified the species provisionally with his 

 C. geniculatus, at least he records Burlington, Iowa, with a 

 query, as one of the localities for his species, and there seems 

 to be no other species of the genus at this locality which 

 could have been indicated by such a reference. Casts, be- 

 lieved to belong to this species, are present in the Chonopec- 

 tus sandstone beds,* but the conditions of preservation are 

 not such as to preserve the delicate surface markings. 



CHONOPECTUS FISCHERl ( N. & P.) 

 PL XII. f. 1 . 



A few imperfect specimens of this typical Chonopectus sand- 

 stone species have been observed in the thin Chonetes bed, 

 but none of them are as well preserved as those from the 

 limestone bed No. 4. 



Rhipidomella burlingtonensis (Hall). 



PI. XII. f. 3. 



A single, nearly perfect specimen of a brachial valve of 

 this species has been collected from the thin Chonetes bed in 

 the Burlington section. It does not differ in any essential 

 particulars from individuals of the same species found at 

 other localities and in other horizons. 



PUGUAX STRIATOCOSTATA (M. & W.). 



Fragments of this species agreeing in all respects with the 

 typical form found in bed No. 4, have been observed in the 

 Chonetes bed. 



* Trans. Ac. Sci. St. Louis. 10: 68. 



