TROCHUS. TOP-SHELL. 187 



from each other, and slightly marked by the line of sepa- 

 ration, depressed and blunt at the tip where there is gene- 

 rally a small perforation, obscurely striate circularly : co* 

 lor mostly dark dull green, with longitudinal waved stripes 

 or zigzag spots or lines of a darker color varying to light 

 or dark purple : the base nearly smooth and more strongly 

 marked with stripes or spots : aperture a little compressed 

 and something angular, perlaceous within : perforation 

 large and deep, reaching to the top, through which it is 

 mostly pervious : the young shells are very flat : diameter 

 three-quarters of an inch ; height nearly as much. 

 On most coasts, v. v. 



3. Trochus cinerarius. Ash-colored Top-shell. 

 Lister, pi. 641. f. 31 Da Costa, pi. 3. f. 6 Donovan, 



pi. 74, two upper and lower fig. Dorset Cat. pi. 16, 

 f. 1 1, 12. 



Shell with five or six spires, which are a little rounded 

 and well denned by the line of separation, tapering to a 

 very fine point which is generally of a chesnut color, dis- 

 tinctly marked with numerous fine raised circular lines : 

 color grey, often of a bjueish or dull crimson cast, with 

 narrow oblique close-set longitudinal brown lines ; the base 

 closely and strongly striate, and appearing as if minutely 

 tubcrcled : aperture a little compressed and somewhat an- 

 gular, perlaceous witjiin, with a small but deep perfora- 

 tion : the young shells are flattish but pointed, with a 

 broad base : diameter five-eighths of an inch j height hardly 

 as much. 



It is easily distinguished from the last by its grey color, 

 especially at the base, by the more distinctly raised volu- 

 tions, the minute brown tip, and regularly striate base^ 

 which is generally a little rough to the touch. 



On most sandy shores, v. v. 



4. Trochus tumidus. T-umid Top~skell. 



Montagu, pi. JO. f. 4 Dow* Cat. pi 16. f. 9, JO 

 fraUter, f. 58. 



Shell conic, with five or six spires, and sometimes sever^ 

 which are well defined and a little flattened at the top of 

 iich,, taperirjg to a Vry fine point,, marked with numerous 



