170 PROCEEDINGS OF THE ACADEMY OF [1890. 



Capulus tribulosus (White). [Plate II, figs. 4a, 4b.] 



F/afyccnis trilnilosum White, 1883. 12th Ann. Rep. U. S. Geol. Sur. Ter., pt. 

 I, p. 186, pi. XLI, figs. 6a, 6b. 



Platyceras trihulosiim Keyes, 1889. Proc. Acad. Nat. Sci., Phila., 1889, p. 290. 



Capulus tribulosus Keyes, 1890. Am. Geol., vol. V. 



Shell rather below medium size, subspiral, rather slendei', forming 

 about one volution ; regularly expanding to the aperture. Apex 

 incurved, far removed from the body of the shell. Aperture ir- 

 regularly oval, usually more or less broadly lobed posteriorly ; lip 

 sharp, irregular, with usually a deep sinus anteriorly. Surface 

 glabrate, but exhibiting numerous fine, closely arranged lines of 

 growth ; also marked by three longitudinal series of long tubular 

 spines, extending from the apertural margin about three-fourths the 

 distance to the apex. Of these spiniferous rows two are disposed 

 laterally, one on each side and the third centrally and dorsally. 



Horizon and locality. Burlington limestone: Burlington, Iowa. 



This is one of the few spiniferous species belonging to the genus 

 Capulus ; and only two others of similar character occur in the 

 American Carbonic rocks. It appears to be closely allied to C. 

 biserialis (Hall) and may eventually prove identical with that form, 

 from which it apparently differs only in having three, instead of 

 two, rows of spines. Thus far it has been noted only in the upper 

 division of the Burlington limestone, when it occurs in the thin 

 sandy-clay partings, associated with delicate and beautifully pre- 

 served bryozoa. The type specimen is not a characteristic repre- 

 sentative of the species, being in several particulars quite abnormal. 

 Capulus acutirostris Hall. 



Capulus acutirostris Hall, 1856. Trans. Albany Institute, vol. IV, p. 31. 



Capulus acutirostris Hall, 1858. Geol. of Iowa, vol. I, pt, ii, p. 665, pi. x.xiii 

 figs, 14a, 14b. 



Platyceras {Capulus) acutirostris McChesney, 1860. Desc. New False. Foss 

 West. Slates, p. 71. 



Platyceras uucuiii Meek & Woithen, 1866. Proc. Acad. Nat. Sci., Phila. 

 1866, p 264. 



Platyceras uncuin Meek & Worthen. 1873. Geol. Sur. Illinois, vol. V, p, 

 516, pi. XVII, fig. 1. 



Platyceras acuti1■ostris\\h\^.(^t\d,\S^'2. Bui. Am. Mus. Nat. Hist., vol. I, p 

 67. 



Platyceras acutirostris Hall, 1883. Indiana Geol. Rept. for 1883, p. 370, pi 

 XXXI, figs. 13-15. 



Capulus acutirostris Keyes, 1890. Am. Geol., vol. V. 



Shell below medium size, rather slender, strongly arcuate, form- 

 ing from one to one and one-half volutions ; posterior side for some 



