20 NOMENCLATURE. 



or membranaceous substance, and varies 

 much in sliape and contexture. 



R.ADU. Rays; elevated strite tending from the 

 centre to the periphery. 



Rostrum. Beak, formed by both lips being 

 produced towards the base into an attenu- 

 ated or narrow process. 



Sipiio seu Sii'HUNCULUS. Siphon ; a small cy- 

 lindrical canal perforating the partition in a 

 chamberedshell, is either ce/z/ra/w, through 

 the centre ; lateralis, through the margins 

 of the partitions j or olliquus, cutting the 

 axis of the wliorls. 



Spira. Spire; the upper whorls collectively. 



cariosa. Carious ; corroded, or, as it were, worm- 

 eaten. 



copltata. Capitate ; terminated by an obtuse 

 head. 



exquisita. Exserted; much attenuated. 



plana. Flat; having the upper whorls of an equal 

 height, so that the spire appears truncate, 



relma. Retuse ; having the lower whorls of tlie 

 fepiie pressed into the body. 



