FOSSILS OF THE BUKLIX.GTON GROUP. 461 



geologists, this one has a more depressed body, larger second radial 

 pieces, a more shallow base, and more numerous arms, which also seem 

 to differ in having very small, pinched nodes along their sides. 



LnrnUty and p<txiti<m Upper part of Burlington division of Lower 

 Carboniferous, at Burlington, Iowa. The specimen figured is numbered 

 215, , in Mr. WACHSMUTH'S collection. 



GENUS PESTREMITES, Say. 

 PEXTREMITES BURLIXGTOXEXSIS, M. and W. 



PI. 8, Fig. 7. 

 Pentremites Burlingtanengis, MEEK and WORTHED, 1869. Proceed. Acad Nat. Sci., Phila. 



BODY attaining a medium size, ovoid, or ovoid-subglo- 

 bose, depressed and short below, and rounded and more 

 produced above. Supplementary base very small, or only 

 one-fourth as wide as the base, rounded and firmly anchy- 

 losed to the true base ; short, or apparently composed of not 

 more than three anchylosed pieces. Base of moderate size, 

 much depressed, or having the form of a pentagonal dish. 

 Eadial pieces once and a-half as long as wide, rather nar- 

 row below and widening upward to near the middle, above 

 which they are very slightly contracted to the top, each di- 

 vided three-fourths of its length, by its rather wide pseudo- 

 ambulacral sinus. Anal and interradial pieces very small, 

 exposed part presenting an elongate-rhombic outline, the 

 upper part being more elongate and acute than the lower. 

 So-called pseudo-ainbulacral areas, wide, moderately con- 

 vex, tapering rather gradually below the middle, and more 

 abruptly above. Pore or arm-pieces, about 35 on each side 

 of each area, less than half as long transversely as the 

 breadth of the exposed part of the lancet pieces at their 

 widest part, nearly transverse above, but becoming some- 

 what oblique toward the lower part of the area; supple- 

 mentary pore pieces small. Lancet pieces exposing a lan- 

 ceolate form, being widest above the middle, gradually 

 tapering below, and contracting abruptly above ; each with 



