70 
gular ridges to the intercostals, and by their lateral surfaces to each other. 
‘They are obliquely truncated at their superior surfaces, excavated, and have a 
horse-shoe-like impression, with a subperforated elevated transverse ridge. 
One of the hexagonal intercostal joints having one of the angular sides of its 
superior surface elongated, has in a specimen in my possession (fig. 1.) a small 
pentagonal interscapulary plate adhering, whose lateral edges connect with 
the lower edges of the scapula, and on whose superior surface another hex- 
agonal interscapulary plate rests. To avoid an increased distance between the 
the arms proceeding from the scapule nearest to this interposed plate, they 
themselves are smaller, and of a contracted form (fig. 5.) I cannot account for 
this apparent irregularity in P. Crassus, but a similar one exists in the next 
species, and in the genera in the division InarricuLaTa. 
The intercostals and scapule where they articulate to each other, must have 
been very muscular, hence a contraction may be traced which produces a 
waved appearance. 
Ihave not been fortunate enough to obtain a specimen extending beyond the 
scapule, but from the occurrence on the same slab, (see plate Poteriocrinites 
Tenuis, fig. 10. and 11.) of joints of the arms, hands and fingers, which, in their 
organic construction, resemble those of the Pentacrinites, I do not hesitate to 
consider these as belonging to this species. I also have found small plates be- 
longing to the integument extending over the cup-like abdominal cavity, and I 
do not doubt its resemblance to that noticed in the Pentacrinites. 
In one instance I have observed a proof of the softness or muscularity of 
the inside of the pelvis, one of its plates having retained the impression of a 
columnar joint, which, by accident, came in contact with it previous to its 
petrifaction. 
