90 UNIVALVES. 



from this circumstance they are sometimes called 

 the Alatae * or winged shells. In some species 

 this expansion is lobed, in others it is divided into 

 curious digitations -f or claws, giving the shells 

 a resemblance to spiders or scorpions, whence 

 they have received their specific names. Some 

 are remarkable for a lengthened spire, and very 

 much resemble in form the Needle Buccinum ; 

 these now constitute the genus Terebra. 



The distinguishing marks of Strombi are the 

 sinus in the outer lip near the base, and the posi- 

 tion of the beak. Like the Cyprseae, they vary so 

 considerably in their different stages of growth, 

 that the juvenile specimens are scarcely to be 

 recognised as belonging to this genus : at an early 

 period the outer lip is not expanded, and there 

 are no traces of claws ; subsequently the wing 

 spreads out, and the claws appear as short open 

 spouts ; and when the shell arrives at its full size, 

 these become solid hornlike projections, often very 

 long and curiously curved. 



There are not more than two or three species 

 of the S trombus found on our coasts. 



The inhabitant is little known, but it is sup- 

 posed from its second sinus or notch, and its 

 curious digitations, that there must be some pe- 

 culiar circumstances in its construction and habits. 



* Alatse winged, from the Latin ala, a wing. 

 + Digitations, projections in the form of fingers, from the 

 Latin digit its, a finger. 



