46 GENUS II. LEPAS. 



Anatifa, a wedge-shaped shell, composed of five or more 

 unequal valves united at the end of a cartilaginous tube, 

 fixed by its base. The aperture without an opercuhim 

 (see Lepas anatifera Linn. pi. 1. /. 2). 

 CoRONULA, a regular sub-conic shell, divided into twelve areas, 

 with an aperture both below and above ; the upper one 

 closed with a four-valved operculum (see Lepas Diadema 

 Linn, pi 1. /. 6). 

 TuBiciNELLA, a tubular univalve, not spiral, narrowing to- 

 Avards the base, truncated at each end. The aperture 

 round, with a four-valved operculum (see Lepas trachece- 

 formis, pi. 1. /. 4). 

 When the valves are marked with lines running from the 

 bottom to the top, they are said to be striated longitudinally 

 (pi. 1. /. 5. a) ; but when the lines are marked the contrary 

 way, they are said to be transversely striated (^pl. 1 . /. 5. h). 

 The strice or lines on the operculum are called longitudinal 

 when running lengthways from the base to the point, or 

 transverse when lying across (as in pi. 1. /. 3). 



