GASTEROPODS 367 



strate its ability to hide itself completely within its house and to 

 close the door very effectively by means of its operculum. The 

 eyes seem to be wanting, or they are concealed under the skin 

 of the head. The shell is usually quite large, with a depressed 

 spire and well-rounded whorls especially the body-whorl, which 

 appears to be greatly swollen. The umbilicus is usually open and 

 moderately large, the lip simple. 



GENUS Polynices (Lunatia, Natica). 



P. heros (generally referred to as Lunatia or Natica heros). One 



of the commonest large shells and one of the most characteristic species 

 of the New England and New Jersey littoral fauna. It is exceedingly 

 common along the Long Island shore, where it may be found on the 

 open beach, in pools with a sandy bottom left by the receding tide. It is 

 usually partially and frequently wholly buried in the sand. The umbili- 

 cus is open and large, the operculum corneous, and the shell heavy and 

 ashy-white to brownish, with (when young) a yellowish epidermis. Its 

 length is from two to four inches. It has no ornamentation whatever. P. 

 heros is a most voracious creature and spends its time in hunting for 

 flesh either alive or dead to devour. It feeds upon dead fish, or 

 upon other mollusks whose shell it is able to pierce by means of its 

 radula, making a little round hole through which it sucks out the flesh 

 from within. The curious egg-cases of this species have already been 

 referred to. (See Plate I.) It glues together particles of sand into the 

 form of a basin with the bottom knocked out and broken on one side. 

 In the gelatinous substance of this basin it deposits its eggs in a regular 

 order. These hatch out in midsummer. Egg-cases of this kind can 

 always be found wherever Polynices lives. For a long time naturalists 

 were greatly piizzled by these curious things, and their blunders are 

 recorded in earlier works, where these egg-cases have been elaborately 

 described as living animals belonging to various invertebrate orders. 

 The largest and best specimens of P. heros are to be found south of 

 Cape Cod. (Page 343.) 



P. triseriata. A small shell of exactly the same shape as P. heros, 

 but decorated with three revolving series of bluish or chestnut spots. 

 It is pretty well determined that this so-called 

 species is only the young of P. heros. It is very 

 abundant all along the coast. 



P. duplicata. This is even more abundant 

 than P. heros. It has a flatter shell, with an obtuse 

 apex and dome-like spire. The umbilicus is 

 partly or wholly closed by a thick, callous, shelly 

 process thrown off from the columellar lip, and is Polynices triseriata, young , 

 chestnut in color. The surface of the shell is f^ 8 n triseriattt ' olller 

 smooth, often polished, ashy-white below and light 



chestnut above. The operculum is corneous. The length of the shell 

 varies in different localities from one half of an inch to about two 



