622 STUART WELLER 



the specimens of S. hannibalensis Swall., from the Louisiana 

 Limestone, in which this angle does not vary much from 6o.° 

 In its fiat cardinal area also the Kinderhook specimens agree 

 with S. extenuatus rather than with S. hannibalensis, in which 

 the area is usually more or less concave. 



15. Aviculopecten sp. undet. A single imperfect specimen of a 

 species of this genus has been observed. It is certainly distinct 

 from any of the species in the Chonopectus fauna at Burlington, 

 and may be an undescribed form. 



16. Pterinopecten cf. P. laetus Hall. Several imperfect specimens 

 of this shell have been observed, which are undoubtedly iden- 

 tical with those so identified from the Chonopectus fauna at 

 Burlington, 1 although it is quite possible that they represent an 

 undescribed species distinct from, but allied to, P. laetus Hall. 



17. Pernopecten cooperensis Shum. This species has as yet not 

 been recognized in the Chonopectus fauna at Burlington, but 

 the Kinderhook specimens which have been observed are indis- 

 tinguishable from specimens occurring in bed No. 5 in the 

 Burlington section. 



18. Leiopteria undulata M. & W. The type specimen of this 

 species, described originally as Pterinea? undulata, 2 is said to 

 have come from the Kinderhook at Burlington, Iowa. The 

 authors of the species state, however, that they "have also seen 

 some imperfect casts, very similar to this species, and possibly 

 not distinct from it, from the same horizon, at Kinderhook, 111. 

 The latter are left valves, and seem to be a little more convex 

 than in the typical examples." The specimens from Kinderhook 

 mentioned by Meek and Worthen were undoubtedly the same 

 as the specimens here under consideration. The species has not 

 been seen by the writer from Burlington, but it doubtless occurs 

 in the Chonopectus fauna at that locality. The figured type 

 specimen is a very imperfect shell, showing parts of both valves; 

 but, so far as it is preserved, it does not seem to differ in any 

 marked degree from the specimens from Kinderhook. 



1 Weller, Transactions of the St. Louis Academy of Sciences, Vol. X, p. 83, 

 Plate 3, Figs. 1, 2. 



2 Geological Survey 0} Illinois, Vol. Ill, p. 456, Plate 14, Fig. 5. 



