No. 19.] ECHINODERMS OF CONNECTICUT. I39 



Furthermore it is often found in coarse gravel, and sometimes 

 beneath large stones. And finally, it occurs not only between 

 tides, where the mouths of its burrows may be exposed to the air 

 for an hour or more, but also below low-water mark, extending 

 to a depth of over loo fathoms. When found in sand between 

 tides its body remains deep in the wet sand beneath the surface, 

 where there is an abundance of water for respiration. 



Its ability of adapting itself to such a wide range in the 

 character of its environment, probably accounts for its very wide 

 geographical distribution. 



The body is long, slender, cylindrical and worm-like, and cap- 

 able of great extension. It is so delicate and fragile that com- 

 plete specimens are difiRcult to preserve intact. Its length is 

 often 4 to 6 or more inches, with a diameter of ^ to ^ of an 

 inch. 



The color of the body is white, often with a distinct tinge of 

 yellow and occasionally of very pale red. The rosy hue of some 

 specimens is due to minute particles of red pigment in the integ- 

 ument, but the reddish color is never so distinct as in the succeed- 

 ing species. The integument is thin and delicate, and often so 

 translucent that the five bands of longitudinal muscles, which are 

 opaque white in color, and certain of the internal organs, can be 

 distinguished in the living animal. This is particularly true of 

 the intestine, which is filled with sand, and of the reproductive 

 organs when the sexual products are mature. 



There are twelve tentacles (Plate XXIX, fig. 3), with char- 

 acteristic branches. Each tentacle commonly consists of a main 

 stalk and five or seven pairs of branches (Plate XXIX, fig. 4), 

 though there are occasionally only three pairs. The branches 

 are tubular or finger-like projections, and are termed digits. 

 Each tentacle has a number of peculiar sense organs on the inner 

 surface near the base. Calcareous deposits, consisting of oval 

 or knobbed plates or rods, occur in the tentacles. 



The most characteristic features of the species of this genus, 

 however, are the very remarkable calcareous deposits found in the 

 body walls. These consist of structures resembling miniature 

 anchors, each of which is connected with a perforated plate of 

 characteristic design (Fig. 28). These occur in all parts of the 



