OF ARTS AND SCIENCES. 285 



A. PROBOSciDALis, Hall, Iowa, Vol. 1, p. 584, PI. 10, fig. 13. 

 Suhcarhoniferous. Burlington limestone. 



A. PTRAMiDATUS, Hall, lowa, Vol. 1, p. 565, non icon. Suhcar- 

 boniferous. Burlington limestone. 



A. PYRiFORMis, B. F. Shumard, Geol. Survey of Missouri, Part 

 2, p. 192, PI. A, fig. 6, a, b. Suhcarhoniferous. Encrinital 

 limestone. 



A. RAMULOSUS, Hall, Iowa, Vol. 1, p. 615, PI. 15, fig. 7. Suhcar- 

 honiferous. Keokuk limestone. 



A. ROTUNDUS, Yandell and Shumard, Geol. Survey of Missouri, 

 Part 2, p. 191, PI. A, fig. 2, a, b. See Chrysty, Letters, 

 PI. 1, fig. 3, 4. Suhcarhoniferous. Encrinital limestone. 



A. SCULPTUS, Hall, Iowa, Vol. 1, p. 582, PI. 10, fig. 11, a, b. Suh- 

 carhoniferous. Burlington limestone. 



A. SUBACULEATUS, Hall, lowa, Vol. 1, p. 570, PI. 10, fig. 2, a, b. 

 Suhcarhoniferous. Burlington limestone. 



A. SUPERLATUS, Hall, Iowa, Vol. 1, p. 572, non icon. Suhcarhon- 

 iferous. Burlington limestone. 



A. sTMMETRicus, Hall, lowa. Vol. 1, p. 574, PI. 10, fig. 8, a, b. 

 Suhcarhoniferous. Burlington limestone. 



A. TENUIRADIATUS, Hall, Palteont. of New York, Vol. 1, p. 18, PI. 

 4, fig. 8, 9. Silurian. This is Palceocystites tenuiradiatas. 



A. TRICORNIS, Hall, Iowa, Vol. 1, p. 569, non icon. Suhcarhon- 

 iferous. Burlington limestone. 



A. TRiNODUS, Hall, Iowa, Vol. 1, p. 575, non icon. Suhcarhon- 

 iferous. Burlington limestone. 



A. TURBiNATUS, Hall, lowa, Vol. 1, p. 587, PI. 11, fig. 1. Suhcar- 

 honiferous. Burlington limestone. 



A. TURBINATUS, var. ELEGANS, p. 588, PL 11, fig. 5. Suhcarhon- 

 iferous. Burlington limestone. 



A. UMBROSUS, Hall, Iowa, Vol. 1, p. 590, PI. 11, fig. 3, a, b. Suh- 

 carhoniferous. Burlington limestone. 



A. UNICORNIS, Owen and Shumard, Geol. Survey of Wisconsin, 

 Iowa, and Minnesota, 1852, p. 593, PL 5, A, fig. 12, a, b. 

 A. unicornis, Hall, Iowa, p. 568. Suhcarhoniferous. Bur- 

 lington limestone. 



A. VENTRicosus, Hall, Iowa, Vol. 1, p. 595, PL 11, fig. 6, a, b. 

 Suhcarhoniferous. Burlington limestone. 



