458 



MARINE INVERTEBRATES 



cutting off his retreat. So tenaciously will they cling to the sand 

 by expanding the muscular foot that the shell may be pulled en- 

 tirely off the body before they will let go. 



GENUS 



E. direclus (Solen ensis, Ensis americanus). 



The common species upon the New England and 

 Jersey coasts. The foot is long, and protrudes from 

 one end of the long shell; it is also very strong, 

 and capable of change at will into almost any form, 

 from a pointed bulb to a flat disk. The siphons, 

 which project from the opposite end of the shell, 

 are short and are not united. The gills are long. 

 The juxtaposition of these organs is at first con- 

 fusing, because the greatly elongated form of the 

 shell and the habits of the animal in burrowing 

 vertically into the sand have caused the foot to be 

 pushed farther away from the posterior portion of 

 the shell and to protrude in a direction just opposite 

 to the siphons. The sheUs are bent or slightly 

 curved ; they gape at both ends ; and they are 

 fitted with very small interlocking teeth at the up- 

 per corner of the posterior end. The color is white, 

 but a yellowish or greenish glossy epidermis covers 

 the entire test. Length about six inches. The 

 manner in which the animal makes its rapid de- 

 scent into the sand is very interesting. First ex- 

 tending the foot lengthwise into a point, it plunges 

 it into the sand ; then, by forcing water into the 

 organ it expands it, thus pushing away the sand on 

 all sides; and still further expanding the foot at the 

 end into a disk, it secures an anchorage which en- 

 ables it to draw down its shell. By quick repe- 

 tition of this process Ensis can get out of sight in 

 a remarkably sudden manner. 



GENUS Solen 



S. viridis. A smaller species, about two inches 

 in length, and with a nearly straight light-green 

 shell. It is often abundant from New Jersey south- 

 ward. 



Ensis directus. S. sicariiis. The common Calif ornian species of 



Northern range. It is only about two inches long, 

 and is rounded anteriorly, but is chopped off squarely behind. It is 

 slightly curved and white, and has a glossy brown epidermis. 



S. rosaceus. Another species of Southern range, very similar in form 

 to the last, but straighter and rosy-white in color. The epidermis is 

 glossy brown. Length two inches. 



