TAYLOR : ON TESTACELLA SCUTULUM. 339 



sometimes even actually concave towards the outer lip, while in T. 

 haliotidea the upper surface is always more or less markedly con- 

 vex. The nucleus is placed at an angle of about 60° or 70° to 

 what may be called the vertical line, while in T. haliotidea the 

 angle formed is only about 45°. The lines of growth are finer 

 and less rugged in scutuiujii, the epidermis is of a brownish 

 color, and the shell generally thinner in substance. The left or 

 columellar side of the shell is more strongly curved — even 

 angular at times — than iv). IiaIiotidea,yi\\\c\\ is more regularly and 

 gently arched. 



On the underside the columella is more strongly arcuate, or 

 almost subangular, and terminates more abruptly, more nearly 

 to the vertical axis of the shell. The projecting apex is seen to 

 be more acute in scutulum, and to perceptibly overhang on the 

 right, whereas in haliotidea it is more central and does not over- 

 hang. The free, thin outer margin is perceptibly darker in color 

 owing to the reddish-brown epidermis being visible through 

 its substance. The muscular scar is crescentic in shape, con- 

 forming in shape to the direction of the lines of growth, and 

 shows also the same pale brownish tint which characterizes the 

 free outer margin. The average size of the shells examined is 

 5 mill, long, by 3 mill, wide, in the broadest part. 



The ANIMAL resembles haliotidea in general form, but is per- 

 haps rather less attenuated anteriorly. It is usually of a tawny- 

 yellow color, varying in depth of tint indifferent specimens, and 

 usually besprinkled with minute brown dots, which are less 

 numerous towards the foot, some specimens are however almost 

 destitute of these markings, while in others, the spots by coal- 

 escence, form more or less distinct and regular brown mottlings 

 on the dorsal surface. The sole is usually of a more or less 

 deep uniform yellow. The lateral furrows are closer together 

 on their emergence from beneath the mantle, than in haliotidea 

 and when the animal is moderately extended, their junction in 

 one common groove may be distinctly seen. The rows of mid- 

 dorsal tubercles so conspicuous in T. viaugei and les^ so in T. 



