214 SMITHSONIAN INSTITUTION 



(?) Meristocrinus tuber osus n. sp. 

 Plate XVII, fig. 6 



I have designated under this name a crushed specimen with 3 IBr and a 

 strongly differentiated tube, which seems to be separated from the basal by 

 another plate; yet the structure is not certain, and the species may not belong 

 here. The radianal is different from that of the generic type, being obliquely 

 to the left of the posterior radial. If the base of the anal series were entirely 

 free on one side this form would be a Gnorimocrinus with 3 IBr, and might be 

 placed under that genus as a variant. 



Type. Riks Museum, Stockholm. 



Horizon and locality. Silurian, Wenlock Group, horizon c; Wisby, Island of Gotland. 



(?) Meristocrinus anceps n. sp. 



Plate XVII, figs. 4, 5 



The two fragmentary specimens in the Riks Museum to which I have given 

 this name have a different anal structure from any of the foregoing. They are 

 of the type having three primibrachs with widely diverging arms, like the last; 

 the radials are much larger and more elongate than in any other species, and the 

 facet does not occupy the entire distal face. The posterior ray is not preserved 

 in either to the first bifurcation, but what I suppose to be the radianal is situated 

 in the oblique position, and it is pentagonal instead of rhombic. It is followed 

 by two good-sized plates meeting the distal faces, and these quickly pass into 

 perisome without any vertical series or transverse line of separation, but with a 

 rather distinctly rounded median prominence. So far as can be seen the two 

 specimens are alike in this respect, and there appears to be a definite anal struc- 

 ture conformable to that of this family. They may not belong to this genus, but 

 there is in them a curious suggestion of structure analogous to what is seen in 

 the two abnormal specimens of M. interbrachiatus (PL XVII, figs, ic and 3b), 

 where -the anal plates tend to pass into coarsely plated perisome without any 

 tube intervening. 



Types. Riks Museum, Stockholm, Sweden. 



Horizon and locality. Silurian, Wenlock Group, horizon d; Wisby, Island of Gotland. 



