HUDSON-RIVER GROUP. 
279 
337. 1. HETEROCRINUS HETERODACTYLUS. 
Pl. LXXVI. Figs. 1 a-o. 
Body short, rounded, subcylindrical, tapering above and below; pelvis composed of 
five small pentagonal plates, which are succeeded by the same number of larger costal 
plates, and these again by five scapulars ; arms irregularly subdivided ; column pentagonal, 
composed of thick joints, which are nodulose at the angles; joints alternating in size as 
they approach the pelvis. 
This is a peculiar species, remarkable for the small size of the body when compared 
with the column. The irregularity of the arrangement of the plates in the arms and 
fingers is likewise a striking characteristic of the species, which is constant in two 
specimens from different localities. In one of the arms (fig. Id), the scapular plate (h ) 
supports a regular series of six or more plates (2- 1 ) of similar form without division. The 
arms at the right and left of this one are again unlike each other. The one on the left has 
three regular and gradually diminishing joints (k 2) above the scapular, and of the same 
form ; the last one supports the cuneiform joint ( k ), which again supports a double row 
of joints ( or a pair of fingers). The arm on the right of the first mentioned, consists of a 
pair of quadrangular joints ( k 3), each of which supports a cuneiform joint (k k). In 
the remaining two arms, no plates have been traced beyond the scapulars, and consequently 
the entire form of the species cannot be determined. Sufficient is visible, however, to show 
the irregular character of the arms, from which its name is given. 
Figs. 1 a , b. Two specimens of the natural size. 
Fig. 1 c. The body of the same enlarged. 1 c'. Transverse section of the column, enlarged. 
Fig. 1 d. An enlarged figure, representing the structure of this species. 
Figs. 1 e, f. Fragments of slate with pentagonal columns of this species, showing the body at/'. 
The fragments of round columns in the same specimens are of another species (see 
Plate lxxvii). 
Fig. 1 g A fragment of one of these columns enlarged, showing the nodulose angles. 
Fig. 1 h. A fragment of a column, with a section of the same. 
Fig. 1 i. A fragment of slate, showing numerous impressions of the discs or plates of the column. 
Fig. 1 k, l , m, 7i, o. The same magnified, showing the pentapctalous expansion around the canal, and 
the deeply impressed striae, which are different in each one. Where the column is crystalized 
these markings are not visible. 
Position and locality. Fragments of the columns of this species are found in the shales 
of the Hudson-river group, in nearly all localities. Of the two individuals figured, one is 
from near Boonville in Lewis county, and the other from Loraine, Jefferson county; it is 
also found near Rome, Oneida county. I have the same species from the shaly strata near 
Cincinnati, Ohio. (State Collection.) 
