80 PROCEEDINGS OF THE ACADEMY OP [1886. 



each side of them a rather conspicuous upright projection, which 

 is truncated at the upper face. These projections are laterally 

 connected in pairs, and eacli pair supports a large interradial 

 plate, which almost covers the whole ventral surface. The five 

 interradials join with one another; they are subtrigonal, their 

 angles truncated ; the upper angle so as to admit a small oral 

 plate, the other two to make space for the articular facet. The 

 sides of the plates along their suture line are beveled, thereby 

 producing along the suture line, in a radial direction, a deep 

 groove, which, evidently, was occupied by the arms in their 

 closed condition. Beneath these grooves there is an opening in 

 the test, at which the ambulacra enter the cal3'x. The openings 

 contain along their median line the ambulacral passage, which is 

 oval in form. At each side of it there is apparently another 

 opening, which Schultze described as " kleine grubenartige Ver- 

 tiefungen," whose functions we cannot understand unless they 

 are in connection with the respiratory apparatus. There is no 

 anal plate ; the anal opening is small, and penetrates the upper 

 part of the interradials close to the oral plate. 



The arms are imperfectly known, but they probably were long, 

 simple, and composed of long joints, like those of the Larvi- 

 formia generally. The articulation upon the radials was by 

 muscles, the axial canals being plainly visible. Column cylin- 

 drical. 



Geological Position^ etc.Haplocrinus seems to have had a 

 wide vertical range, three species being from the Devonian, the 

 fourth one, according to De Koninck, from the Carboniferous (?). 



The following species have been described : 



1862. Haplocrinus clio Hall, 15th Rep, N. York State Cab. Nat. Ilust., p. 14:'., PI. 1, 

 figs. 5-9. -Maroellus Shale. Onondago Co., N. Y. 



1868. H. granatum De Koninck, Bull. d. I'Acad. Roy. de Belg. (Ser. 2), Tome iii, 

 No. 4, PI. 5, figs. 6-10. (?) Mountain limcst. Eolland, Yorksh., England. 



1826. H. mespiliformis (Goldfuss), Eugeniacrinites mespiliformis, Petref. Germ., 

 i, p. 2\?>, PI. 64, fig. 6. Haplocrinus spaeroideus, 1834, Steininger, Bull. 

 Soc. Geol. de Prance, Tome viii, p. 2:i2. Haplocrinus mespiliformis F. 

 Roemer, 1844, Rhein. Uebergangsgeb., p. 16; also Leth. Geogn., 1855 

 (Ausg. .3), p. 26L Pictet, 1857, Traite de Pal6ont., iv, PI. c, fig. 2. Bronn, 

 1860, Klassen d. Thierreichs (Actinozoa), PI. 28, fig. 4 A-C Dujardin and 

 Ilupe, 1862, Hist. Nat. des Zoophytes Echinod., p. 105, PI. 5, fig. 9. 

 Schultze, 1866, Echin. Eifl. Kalk., p. 104, PL 12, figs. 10, 11. Devonian. 

 Eifel, Germany. 



1844. H. stellaris Roemer, Rhein. Uebergangsgeb., p. 6;'., PI. ?>, fig. 5 ; also Sand- 

 berger, Jahrbuch,.1845, p. 777. Roemer, 1855, Lethaea Geogn. (Ausg. 3), 

 p. 261. Devonian. Nassau, Germany. 



