162 CATALOGUE OF THE BLASTOIDEA. 



1. Calyx robust in every respect, and the base broader. (PI. II. fig. 14.) 



2. Calyx narrow and slim, both the summit and base more or less attenuated. 

 (PI. II. fig. 15.) 



The first of these two forms appears to approach the more nearly to Shumard's 

 original figure. 



Locality and Horizon. Burlington, Iowa: Upper Burlington Limestone, Sub- 

 carboniferous. 



Pentremites coxoideus, Hall. 

 (PL II. figs. 16-23; PL III. figs. 4-12 ; PL XVIII. figs. 6-8.) 

 Pentremites conoideus, Hall, Trans. Albany Inst. 1856, vol. iv. p. 5 ; Iowa Geol. Report, 



1858, vol. i. pt. 2, p. 655, t. 22. f. 8-10. 

 Pentremites Koninckana, Hall, Trans. Albany Inst. 1856, vol. iv. p. 4; Iowa Geol. Report, 



vol. i. pt. 2, p. 656, t. 22. L 11, a-c. 

 Pentremites conoideus, Shumard, Trans. St. Louis Acad. Sci. 1858, vol. i. pt. 2, pp. 243 and 



246, t. 9. L 4. 

 Pentremites conoideus et P. Koninckana, Shumard, Trans. St. Louis Acad. Sci. 1865, vol. ii. 



no. 2, pp. 383 and 384. 

 Pentremites conoideus, Billings, American Journ. Sci. 1869, vol. xlviii. p. 81. f. 15. 

 Pentremites sulcatus, Zittel, Handb. Pal. 1879, 1 Bd. 3 Lief. p. 432, f. 305 a. 

 Pentremites conoideus, White, in Collett's 2nd Ann. Report Dept. Stat, and Geol. Indiana, 



1880, p. 512, t. 7. f. 12. 

 Pentremites conoideus, et P. Koninckana, Whitfield, Bull. American Mus. Nat. Hist. 1882, 



vol. i. no. 3, pp. 43 and 44, t. 9. figs. 32 and 33. 

 Pentremites conoideus, ct P. Koninckana, E. & C, Ann. & Mag. Nat. Hist. 1882, vol. ix. 



p. 216. 

 Pentremites conoideus, et P. Koninckana, Hall, in Collett's 12th Ann. Report Dept. Geol. 



and Nat. Hist, for 1882 [1883], p. 323, t. 32. 

 figs. 32 and 33. 



Sp. Char. Calyx conoidal or pyramidal, gradually contracting upwards from the 

 radial lips, but in the young state subglobose or subpyriform ; summit more or less 

 contracted or acuminate, but in the young condition blunt, convex, and relatively 

 broad ; base subtruncate or subpyramidal ; section pentagonal, and very strongly so at 

 the radial lips in the adult ; periphery at the radial lips, though in the adult this line 

 is but little above the subtruncate base. Basal plates forming a very shallow cup, 

 almost flat internally, but in the immature condition the cup is moderately deep, and 

 when viewed from below rather trilobate, liadial plates oblong, much arched 

 transversely, a little less than two thirds the entire length of the calyx when fully 

 grown ; bodies small, nearly horizontal, and turned in to assist in forming the sub- 

 truncate base, but in the young state the bodies are inclined at a much sharper angle 

 to the vertical axis of the calyx ; limbs long and steep sided, their margins parallel 

 and obliquely truncated above, but in the immature condition the limbs and bodies 



