Brachlocriuus and Jlerpetocrinus. — Bather. 215 
lerlcrinus; and it is no unusual thing to hear of stalked erin- 
oids attaining to a semi-locomotor existence. 
Next, to show that the remains called BrachliK'riinis nodo- 
sdt'ins are referable to Herpetorriaua. The coiling of the 
stem, as in plate V, figure 7, is notoriously characteristic of 
that genus; so also are the paired cirri, which give the stem 
the semblance of a pinnulate arm. The slight groove on the 
inner curvature, represented in plate VI, figure 1, isalsofovmd 
in all species of Ilerpetocriniis, while the section, plate VI, 
figure 3f?, may be compared with the numerous sections figured 
in "The Crinoidea of Gotland," text-figure 12 and plates I 
and II. 
It is true that in the excellent drawings by F. B. Meek, 
which adorn Prof. Hall's volume, one cannot see any of the 
minuter details and anatomical structures which a prolonged 
study of a very large number of Swedish and English speci- 
mens has enabled me to demonstrate in my memoir. There 
may, therefore, still be room for doubt as to whether the spe- 
cies is actually a Herpetocriuus. Mr. Charles Wachsmuth 
informed me some time ago that Herpetocrinus-\\\!i.ii forms oc- 
curred in an order of crinoids other than the Inadunata ; so 
that Brackiocrinn.s might conceivably be generically distinct 
from Herpetocriints. I cannot, however, think that this is 
really the case. So far as I understand, the forms alluded to 
by Mr. Wachsmuth are of Carboniferous (or Subcarboniferous) 
age ; whereas the true Herpetocrinus is confined to the Silu- 
rian. The three species as yet described in North America 
come from the Niagara group, corresponding to the English 
Wenlock, in which also the genus is well developed. Brachi- 
ocrinus tiodosai'ius is from a higher horizon — the Lower Hel- 
derberg. But in Gotland, species of JJerpeforrfints occur in 
beds of the same age, so that this presents no difficulty. On 
the contrary, the geological horizon is just what the appear- 
ance of the species would lead one to ex])('ct. It is a pecu- 
liarly developed species, more removed from what may be re- 
garded as the ancestral form than are the species from lower 
horizons. Its cirri are distinctly curious, "com])f)sed of thick 
bead-like joints, whicii iiici-ease in size from tlic ])ase to tiie 
middle, and thence diminish to the extremities." This char 
acter is possessed by only one other species of //erjtefocr/inis, 
