290 PROCEEDINGS OF THE ACADEMY OF [1881. 



Anal area wider ; the first plate in line with the first interra- 

 dials, perhaps a little larger, succeeded by three plates in the 

 second, and a like number in all superior series. 



Yault only known in M. Garleyi, where it is low, scarcel}' 

 rising beyond tlie horizon of the calyx, 



Interradial regions depressed and excavated between the raj'S, 

 thereb}' giving to the form a pentalobate outline. 



Radial portions prominent, toward the margin of each arm dis- 

 tinctly elcA'ated and formed into a rounded ridge. 



Arm openings arranged along the margin of the vault, directed 

 upwards. The vault is composed of very minute, irregular pieces 

 without definite arrangement, even the apical dome plates are 

 obscure. 



Anal aperture excentric, opening directly through the vault. 



Form of column unknown ; central canal subpentagonal and 

 of more than medium size. 



Geological Position, etc. — Mariacrinus is confined to the Upper 

 Silurian, and occurs in Europe and America. 



We recognize the following species . — 



*1S7S. Mariacrinus angustatus Angclln. (Melocr, angustatus.) Iconogr. Crin. 



Suec, p. 20, P). 2fi, fig. 22. Upper Silur. Gothland, Sweden. 

 *18G3. Mariacr. Carleyi Hall. (Glyptocr. Carleyi.) Trans. Albany Inst., iv, p. 



203,- also 28th Rep. N. Y. St. Cab. Nat. Hist., 1875, PI. 14, figs. 7-10. 



Niagara gr. Waldron, Ind. 

 *1863. Hariacr. ob.COnicus Hall. (Melocr. obconicus.) Trans. Albany Inst., p. 



206.; also 28th Rep. N. York St. Cab. Nat. Hist., 1875, PI. 14, figs. 11-14. 



Niagara gr. Waldron, Ind. 

 1859. Mariacr. plumosus Hall. (Type of the genu!=.) Paleont. N. York, iii, p. 110 



PI. 3, figs. 6-11. Lower Helderberg gr. Herkimer Co., N. Y. 

 1859. Mariacr, ramosus Hall. Paleont. N. York, iii, p. 147, PI. 2, figs. 2, 3. Lower 



Helderberg gr. Herkimer Co., N. Y. 



8. TECHNOCRINUS Hall. 



1859. Hall. Paleont. New York, iii, p. 139. 

 1879. Zittel. Uandb. der. Palaeontologie, i,. p. 372. 



According to Hall, Technocrinus differs from 3Iariacrinus 

 only in the arm structure, he therefore at first arranged it sub- 

 generically under that genus. A careful comparison of Techno- 

 crinus, not only with that section of Hall's J/armcWnMs which we 

 have referred to Melocrimis, but also with Mai^iaciHuus plumosus 

 the present type, has convinced us that Technocrinus difters in 



