GEROULD: CAUDINA. 135 
The leg of the calcareous table is developed upon the primitive 
X-shaped spicule, the arms of which are curved inward toward the 
axis of the animal; they form the attached end of the leg. From 
about the middle of that side of each arm which faces the surface 
of the body arises a single rod, which branches dichotomously in a 
direction parallel to the margin of the disc (Fig. 35). These 
branches subsequently unite to form the basis of the free extremity 
of the leg. 
The calcareous tables are found in the integument of all parts 
of the body except the buccal region, the tentacles, the anterior part 
of the body immediately behind the tentacles, and a small circum- 
anal area. They lie in a single layer in the outer part of the 
connective tissue of the body-wall and are so abundant that the 
edges of the discs of adjacent tables overlap each other slightly 
during muscular contractions of the body-wall. 
Through the kindness of Mr. Agassiz I have had an opportunity 
to examine the integument of specimens of C. arenata var. armata 
Théel, dredged in the Blake expedition (Plate 3, figs. 34-57). 
Théel (86) has already given a good general description of these 
calcareous tables, but without figures. They are several times as 
large as those of C. arenata Gould, and differ from them markedly 
inform. The disc is smooth and commonly of a somewhat trian- 
gular shape, though it may be more or less elliptical or quadran- 
gular; the margin is uneven, and there are between twenty and 
thirty perforations in each disc. The spire or leg is composed of 
three rods, as Théel has described it. These have numerous spinous 
processes upon them and are united to one another, as in C. arenata, 
near the base as well as at the extremity. The following measure- 
ments give a fair idea of the range in size and proportions of the 
disc: 150 » x 270 p, 165 pw x 260 p, 240 » x 260 p, 245 w x 265 uw. 
The length of the leg is about 155 p. 
The calcareous bodies of the variety armata are distributed in the 
integument in the same way as in the type-form. Those found in 
the tail region, near the anus, are similar to those found in the trunk. 
4. MUSCULATURE. 
The musculature of the body-wall of Caudina, like that in other 
holothurians, consists of (1) longitudinal muscles, radial in position, 
and (2) transverse muscles, interradial in position. 
