252 APORRHAID^. 



of Pctiver, " aile de chauve-souris femelle " or '' patte 

 d^'oye '' of D^Avila^ and ^' zamarugola ^^ of the Venetians, 

 by the poorer class of which people the animal was — 

 perhaps is still — eaten. According to Mr. Couch, So- 

 laster papposus also reckons it an agreeable kind of food : 

 when the soft portion has been digested, the empty shell 

 is rejected, and becomes the habitation of a Sipunculus, 

 which narrows the too capacious entrance with aggluti- 

 nated sand. Specimens from deep water are smaller 

 than those from the coast. The top of old but living 

 shells which had lost their upper story is sometimes 

 closed by a semispiral plug or septum of new shelly 

 matter ; the apex is very seldom perfect in full-grown 

 specimens. When the outer lip is complete the sub- 

 sequent growth takes place by adding fresh layers inside ; 

 so that tlie age of the individual is probably shown by 

 the number of such layers. In immature specimens 

 the commencement of the pterygoid or wing-like flap 

 of the outer lip is defined by a rib of enamel along the 

 mouth, which likewise lines the canal at the base as 

 well as the upper process of the flap. Still younger 

 specimens, before any sign of the flap appears, have the 

 outer lip flexuous, with a wide and deep sinus at the 

 upper part, and a long straight canal at the base. In 

 this stage of growth they strongly resemble Fast. The 

 fi'y form a short cylinder. Monstrosities are not un- 

 common, especially in the shape and relative size of the 

 digitated processes ; the basal point, however, is always 

 formed like a spear-head. 



Da Costa altered the specific name to quadrifidus. 



