LECANOCRINIDAE IC)3 



Mespilocrinus forbesianus De Koninck and Le Hon 



Plate V, figs. 1-3 



Young Poteriocrinus Phillips, Geol. Yorkshire, 1836, p. 205, pi. 4, figs. 5, 6. 



Mespilocrinus forbesianus De Koninck and Le Hon, Recherch. Crin. Carb. Belgique, 1853, p. 112, pi. 2, 

 figs. la-c. — Pictet, Traite Paleontologie, IV, 1857, p. 320, pi. 100, fig. 19. — Beyrich, Monatsber. 

 Akad. Wiss. Berlin, Feb., 1871, p. 46 (Transl. in Ann. and Mag. Nat. Hist., (4) VII, p. 403. — 

 Quenstedt, Petref. Deutschlands, IV, 1876, p. 516, pi. 108, fig. 28. — Wachsmuth and Springer, 

 Revision Palaeocrinoidea, pt. I, 1879, p. 42. — Springer, Jour. Geology, XIV, 1906, p. 523, pi. J, 

 fig. 14. 



Type of the genus. 



A large species. Crown subglobose, height and width about equal ; spread 

 of calyx from base to top of RR, i to 2.5; height to width at RR, 1 to 2. Base 

 rounded. Surface smooth. Folded crown in maximum specimen, 14 mm. high 

 by 14 mm. wide. 



IBB small, visible in side view. BB large, post. B much the largest, reach- 

 ing to full height of RR. Anal x short and broad, filling the interradius. RR 

 somewhat unequal, and asymmetric ; height of B to R to IBr, 4.2 : 3 : 1.7. IBr 2 ; 

 IIBr 2 or 3; all Br relatively short and wide. Rays and arms broadly rounded, 

 in close lateral contact, and twisting to the right as seen from the base; infold- 

 ing soon after second bifurcation; the two posterior rays arching over the anal 

 plate. Column large, cylindrical ; proximal columnals short, slightly increasing 

 downward, becoming uniform in size and shape as far as preserved. 



The above description is to a considerable extent a repetition of generic characters. The 

 proportionally large primibrachs distinguish the species from several others, and the column 

 from all in which it is known. Here the column is a straight-sided cylinder, with no depres- 

 sions at the sutures, nor bulging in the middle of the columnals which are relatively short ; 

 it represents the one extreme from which, with some gradations, we pass in other species to a 

 column about as different as could possibly be imagined. The species is extremely rare in 

 its original locality in Belgium. De Koninck had two specimens, and I know of only two that 

 have been found since his time, one of them being the fine specimen with long stem in the 

 British Museum (PI. V, figs. 3a, b). This or a similar species occurs in England; the small 

 specimen figured by Phillips as a young Poteriocrinus from the Mountain limestone of 

 Yorkshire evidently belongs to the genus. 



Type. De Koninck and Le Hon's original specimens are in the Royal Museum at 

 Brussels. The other specimen here figured is in the British Museum. 



Horizon and locality. Lower Carboniferous, Mountain limestone ; Tournai, Belgium. 



