48 IOWA STUDIES IN NATURAL HISTORY 
thick, inversely conical, bent towards one side, of a hard, semi- 
calcareous substance, having under a magnifier a very delicate 
shagreen-like appearance. There are no sutures discernible with 
certainty, though in some parts there appear to be faint in- 
dications of them. I did not feel justified in making attempts 
to render them more apparent by preparation. There are two 
rows of blunt tubercles on the body part, corresponding to the 
middle of each arm; a small tuberculated area is also noticeable 
near the border of the calicle between these rows, and scattering 
tubercles are found over other parts of the body. Ten arms 
originate in pairs from five axial joints; the original specimen 
of d’Orbigny is described as having had but eight, and was 
certainly anomalous. The axial joints are pentagonal with 
rounded angles, hemispherically swollen and tuberculated in the 
middle, closely joined to each other laterally; the tubercles on 
these joints are in three irregular rows, one in the middle and 
one corresponding to the middle of each arm. The inside of 
these joints is deeply channeled in the middle. The arms are 
composed of thick, short joints, wedge-shaped, swollen and 
tuberculated; the articulations form a deep transverse furrow. 
There are no syzygies. When contracted the arms are rolled in 
a spiral, and pressed laterally against one another so as to en- 
close a hermetically closed cavity. At the eighth or tenth joint 
the arm contracts suddenly, and becomes wedge-shaped outside, 
so as to fit more closely against its neighbors, the rest of the 
arm being rolled up inside of the cavity. The cirrhi of the 
arms are formed of broad, flat joints, fitting also closely to their 
neighbors, and rolled up spirally towards the ambulacral chan- 
nel of the arm when contracted. The mouth is surrounded by 
five triangular plates, by which it can be apparently almost or 
entirely closed. These pieces are deeply and irregularly cor- 
rugated on the outside. The intervals of the plates or angles 
of the mouth correspond to the ambulacral channels. There is 
a small triangular plate in one of the interambulacral spaces 
inside of the axial joints, which is probably an anal plate, but 
no opening can be detected near it. The internal or digestive 
eavity could not be examined. 
‘‘The specimen was obtained at Barbados by a fisherman, 
who brought it from deep water upon his hook; it has lost four 
of its arms, but is otherwise complete. It is dry and of black 
color, somewhat lighter on the arms. The whole specimen in 
its contracted state is about one inch and three-fourths high.”’ 
From a comparison of the figures it seems reasonably certain 
that the peculiarly distorted specimen described by Pourtalés 
was the same as that mentioned by Gray for which he suggested 
the name Holopus rawsont. 
