SEA-CUCUMBERS 233 
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rows of tube-feet lie near together, on a flat under surface, and form a 
kind of sole on which the animal creeps. The oral end of the body is a 
little raised and bears ten tentacles; these tentacles are profusely and 
finely branched, and when expanded are about as long as the body. 
The aboral end is obtuse and a little raised. Around the oral and anal 
openings the scales are grouped, forming circles in those regions. This 
holothurian is bright red in color, and when expanded is a beautiful 
object, perhaps the most attractive in appearance of any in the class. 
When retracted it has the aspect of an ascidian, and for a time was 
supposed to belong to that group. It is found on the New England coast 
on the under side of large shelving rocks. 
ORDER APOLDA 
Genus Synapta 
S. tenuis. This curious animal is long and slender, and so transpa- 
rent that its internal organs are clearly visible. Around the mouth area 
circular tube and a wreath of twelve branching tentacles. There are no 
ambulacra. Little spots scattered irregularly over the surface show, 
when highly magnified, small warts, each one of which has a calcareous 
projection shaped like a little anchor. By means of these anchors and 
by the contractions of its body the animal moves through the mud or 
sand in which it lives, near low-water mark. The sand is collected into 
rings at the oral end and pushed downward until the whole animal is 
inclosed in a sand-tube. When empty Synapta is white and transparent, 
and the digestive canal may be seen wound in a spiral throughout its 
length ; but when gorged with food, sand, pebbles, and shells can be 
distinctly seen filling the food-canal, and the body then has a dark- 
gray color. Synapta grows to a length of eighteen inches or more, but 
is constantly breaking pieces off its posterior end by muscular contrac- 
tions. When kept in confinement it soon commences to constrict its 
body at various points, and after a few hours there is nothing left but a 
mass of fragments. It is viviparous, that is, it carries its young in the 
body-cavity ; the eggs are hatched, and the young approach maturity 
before they are expelled. This species ranges from Cape Cod to North 
Carolina, and can be found in the upper part of its burrows when the 
tide is out. 
S. roseola. This species occurs in the same localities as S. tenuis, and 
differs from it mainly in color, which is pale red, due to minute red spots 
scattered through the skin. 
S. rotifera. A speciesfound in Florida. It is light purplish in color, 
and has eight or ten branches on each of the twelve tentacles. In this 
pas the spicules of lime in the skin are shaped like wheels instead of 
anchors. 
Genus Caudina 
C. arenata. About four inches long and tapers to the ends; the 
posterior end sometimes narrowed to a long, slender, tail-like extremity ; 
tentacles around the mouth resemble cloves. It lives in sand and may 
be found on the New England coast, washed ashore after a storm. 
