MvsCKIITloVs OF THE SPECIES. L99 



which we were formerly inclined to refer to Troostocrinus on account of Its extremelj 

 elongate form and narrow summit. But wc have since seen specimens either of this 

 species or of P. gemmiformis, Hambach (if, indeed, (hey are not identical), and we 



find that it is a line J'ciitn •tuiti s, which passes on the one hand into Pentremitidea 

 and the Troostoblastida\ and on the other info such forms of P. piriformis as un- 

 represented on PI. 11. figs. 28, 30. Hambach lias already pointed this out, and we 

 are glad to be able to agree with him. 

 Type. Pentremites lineatus, Shumard. 



Metablastus linbatus, F. B. Shumard, sp. 



(PL III. figs. 14, 15; PI. XVII. fig. 18.) 



Pentremites (meatus, Shumard, Trans. St. Louis Acad. Sci. 1858, vol. i. no. 2, pp. 241,247, 



t. 9. f. 3, «, b. 

 Troosticrinus {Pentremites) lineatus, Shumard, ibid., 18G5, vol. ii. uo. 2, p. 384 (and note). 

 Pentremites liiK-iitiia, White, Boston Journ. Nat. Hist. 1863, vol. vii. no. 1, p. 488. 

 Troostocrinus lineatus, E. & C, Ann. & Mag. Nat. Hist. 1882, vol. ix. p. 2 1'.). 



Sp. Char. Calyx elongately subf'usiform ; summit very much contracted, and trun- 

 cated obliquely outwards ; base roundly pentagonal above, rapidly tapering down- 

 wards to a narrow trihedral extremity ; section above the lips distinctly pentagonal ; 

 periphery one third from the summit. Pasal plates elongate, slender, rounded above 

 but subangular below ; interbasal sutures on the flat sides. Radial plates very long 

 and narrow, increasing but little in width, bodies and limbs as nearly as possible of 

 equal width ; bodies arched and angular in the middle line, sides flattened, limbs 

 lanceolate; lips not produced; sinuses very narrow and deeply cleft; interradial 

 sutures in very slight concavities. Deltoid plates appearing round the summit as 

 strong crests overlapped by the radial limbs ; radio-deltoid sutures almost vertical on 

 the sides of the sinuses. Ambulacra very narrow, linear, and one third the length of 

 the calyx, deeply set in the sinuses; side plates fifty; lancet-plate with three canals 

 arranged in a triangle. Hydrospire-folds four on each side of an ambulacrum ; sacs 

 pyriform ; spiracles linear. Mouth small, very much contracted. Anus a large oval 

 opening in the posterior deltoid with somewhat thickened edges. Column circular. 

 Ornament of microscopic lines arranged parallel to the margins of the plates. 



Remarks. Shumard : has given a good description of this species, so far as it could 

 be made out from a somewhat crushed specimen, but the structure of the summit has 

 hitherto been entirely unknown. There is, however, a good though slightly crushed 

 example of it in Mr. Wachsmuth's collection, which shows the ten linear spiracles and 

 the unusually large anal opening (PL III. figs. 14, 15). Neither of these views, how- 

 ever, is adapted for showing the radio-deltoid sutures, which have an altogether 

 different position from that assigned to them by Shumard. They arc shown in his 

 figure as appearing on the exterior of the calyx above the truncated ends of the radial 

 1 Trans. St. Louis Acad. Sci. 1S5S, vol. i. no. 2, p. 241, pi. ix. fig. 3. 



