78 POPULAR BRITISH CONCHOLOGY. 



shell has a cartilage-pit in tlie hinge, two broad diverging 



teeth, and no external ligament. The shell of 



M. ferruginosa is really white, long, oval, smooth; 



M. bideyitata, white, rather squarish-oblong; 



M. suhstriata, small, brown, striated obliquely, short. 



The latter species is generally found attached to the spines 

 of the purple Sjoatangus, or " sea-urchin/^ By means of its 

 byssus, or cable, it is fixed so firmly in its position, that it 

 is difficult to remove without breaking the delicate shell; 

 yet in spite of this power of firm adherence, the Montacuta 

 could not take the motto " always at home,^' for its powers 

 of locomotion are remarkably great for so minute a creature, 

 and are doubtless exercised often. When on the move, it 

 stretches out the rounded point of its foot, and taking firm 

 hold, draws itself up, and rapidly repeating the act, gets 

 quickly over the ground. 



II. TuRTONiA minuta has one thin siphonal tube at the 

 short end, and the foot long and sharp, exserted from the 

 opposite. The shell is very small, oval, brown, with the 

 ligament outside, and two minute teeth in the front part of 

 the hinge within. " It inhabits pools and crevices of rocks 

 between tide-marks,^^ sometimes adhering to little corallines. 



III. Kellia has one very short siphon at the back and 



