descriptions of Tin: spkciks. 287 



very numerous in 0. vents. 0. stelliformis is said to possess fifty, and there are 

 twenty-two in 0. gracilis. There are at least twenty-five in 0. pentangularis, and 

 something under twenty in 0. Orlignyanus (PI. XI. fig. 10). 



The length of the hydrospire-clefts or spiracles is a variable character. They are 

 shortest in 0. stelliformis (PL XI. fig. 8, { .) ; PI. XV. fig. 11), but extend along 

 nearly the whole length of the ambulacra in <). pentangularis and 0. verus (PI. XV. 

 figs. 2, 8), and entirely so in 0. Orlignyanus (PL XIV. figs. 16-18). The hydrospires, 

 so far as we are acquainted with them, vary from four to twelve in number. There 

 are five in 0. stelliformis, from seven to twelve in 0. verus and 0. pentangularis 

 (PL XVII. figs. 12-14), six in 0. Orlignyanus (PL XL fig. 10), and at least four in 

 the other Belgian species, 0. Puzos. 



Species. The following are the species which we refer to Orophocrinus : — 



Codonites campanulatus, Llambach. Burlington Group, Subcarboniferous ; Iowa. 

 Codonites gracilis, M. & W. Burlington Group, Subcarboniferous; Iowa. 

 Pentremites Orlignyanus, de Koninck. Carboniferous Limestone; Belgium. 

 PI atycrinus pentangularis, Miller (pars). Carboniferous Limestone ; Lancashire, 



Ireland, and Belgium. 

 Orophocrinus prcelongus, Baily. Carboniferous Limestone ; County Dublin. 

 Pentremites Puzos, Minister. Carboniferous Limestone ; Belgium. 

 Pentremites stelliformis, O. & S. Burlington Group, Subcarboniferous ; 



Missouri, Iowa, Illinois. 

 Mitra vera, Cumberland. Carboniferous Limestone ; Lancashire. 



Distribution. From the above list it will be seen that Orophocrinus is entirely 

 confined to rocks of the Carboniferous period, occurring, however, in those of 

 England, Ireland, Belgium, and America. It thus has a wider geographical distri- 

 bution than any of the other genera found in Britain, with the single exception of 

 Phamoschisma. 



Type. Pentremites stelliformis, Owen and Shumard. 



Orophocrinus stelliformis, Owen and Shumard, sp. 1 

 (PL XI. figs. 8, 9 ; PL XV. figs. 11-15 ; PL XVI. figs. 5-7 ; PL XVII. fig. 12.) 

 Pentremites stelliformis, O. & S., Journ. Acad. Nat. Sci. Philad. 1850, vol. ii. pt. 1, p. 67, 



t. 7. f. 16 a & b. 

 Pentremites stelliformis, O. & S., Wisconsin, Iowa, and Minnesota Geol. Report, 1852, p. 593, 



t.v. a, f. 16 a & b. 

 Pentremites stelliformis, White, Boston Journ. Nat. Hist. 1863, vol. iii. no. 4, p. 486. 



1 Dr. C. A. White appears to consider his Pertiremites Sirirts (Proc. Boston Soc. Nat. Hist. 1862, vol. ix. 

 no. 2, p. 20, f. 3) as congeneric with 0. steMfbrmis (Boston Journ. Xat. Hist. 18G3, vol. vii. no. 4, p. 486), and 

 Mr. Waehsmuth has given us a hint to the same effect ; hut White's description and figure alone do not 

 convey this idea to our minds at all. 



