28G 



9. 

 Umbilicatus, Trochus umbilicaris. Br. ZooL t, 80. f. 106. 



Lijier. Conch, t. 640. f. 29 ? 

 Chem. Conch, v. t. 171 f. 16S5. 

 Trochus umbilicalis. Da. Cojla. p, 46. t. 3. f. 4. 4. 

 Troclius cinerarias. Pidt. Cat Dorfet. p 44. 



Don. hr. Shells, iii. t. 74. three middle 

 figures. 



o^ 



T. with a ftrong, flattifh fiiell, rounded at the top; the 

 apex depreffed, and not pointed: the volutions are five, 

 nearly even, defined only by a fine, thread-like line, and 

 wrought with nearly obfolete fpiral ilriee : colour white, 

 or greenifh, marked with longitudinal, waved, or zigzag 

 lines of a light or dark purple : aperture compreffed, an- 

 gulatcd : umbilicus large, and perforated to the apex. 

 Diameter, at the bafe, three-quarters of an inch ; height 

 not five-eighths of an inch. Young iTiells are extremely 

 flat; thofe of three-eighths of an inch at the bafe, fcarce 

 rife in height one eighth. 



No two fliells feem to have puzzled conchologifis more 

 than this and the preceding, and even the later authors 

 have heaped confufion upon confufion ; fome have made 

 them the fame, others have reverfed their trivial names, 

 or multiplied them into three diftinft fpecies, from fome 

 accidental markings. Mr. Penn\nt, though very con- 

 cife, feems to have defined the diftinftion pretty well ; but 

 has erred in marking this fliell the umbilicaris of Lin- 

 N.EUs; that fpecies is very different, and not found in 

 England. 



Upon 



