PAL.EOTEOPUS THOMSONI. 55 
In the laro-er specimens of Palceotropus Josephince there is a sHght tendency 
to the formation of very rudimentary bourrelets. The larger outer plates 
of the actinal system carry a few minute miliary tubercles and spines. (PI. 
XXIII. Fif. 14.) On the abactinal surface the ambulacral suckers are 
slender, surmounted by a small indistinct sucker, the tentacles increase in 
size towards the ambitus, and near the actinostome there are four or five 
large fimbriated tentacles in each ambulacral area. 
The pedicellaria3 are most varied, representing types characteristic of the 
Clypeastroids as well as the Spatangoids. On the actinal side there are in 
the ambulacra, near the outer edges, minute slender, long-stemmed, two- 
jointed pedicellaria3 with small pear-shaped trifid heads. At the ambitus, 
interspersed among the preceding, are short-stemmed, large-headed, stout 
pedicellarice resembling the Clypeastroid types. In the bare interambulacral 
spaces there are a few large-headed, short-stemmed, trifid pedicellariaj, some 
with short prongs, others with long crossing prongs. Scattered irregularly 
over the abactinal surface are few distant triangular-headed trifid pedicel- 
larifB, with long, slender stems, and short, flexible head-joints. The heads 
of these last pedicellariaj are of two very different sizes, but otherwise they 
do not differ. 
* Palaeotropus Thomsoni A. Ac. 
Palaeotropus Thomsoni A. Ac. Bull. M. C. Z., VIIL, No. 2, p. 80, 1880. 
Lat. 32° 43' 25" X., Lung. 77° 20' 30" W. 233 fathoms. 
At Station 321 a single broken specimen of this species was collected, 
which differs most strikingly from all the other specimens of PalfBotropus. 
It is closely covered by uniform tubercles on the abactinal side. It has a 
proportionally greater number of coronal plates, and a high test, with a 
keeled posterior interambulacral median line. Apex more posterior than in 
P. Joscphinct}. 
The color of the test is yellowish white when alive. The large P. Josepldnce 
are of a dirty greenish red color, and when young more pinkish. This 
species is also remarkable for its broad, bare posterior lateral ambulacra on 
the abactinal side, and for its prominent keeled, very elongate actinal plas- 
tron, and its longitudinally elongate anal fascicle, still very prominent at a 
time when in P. JoscpJitnce the posterior extremity has become flattened, and 
the fascicle quite indistinct. 
