Descriptions of some Australian Phyllopoda. 37 



the length, and occnrring considerably in front of the middle. 

 The dorsal margin is boldly curved in front, but posteriorly 

 becomes almost straight, and slopes rather steeply towards the 

 hind extremity. The ventral margin is evenly curved and 

 passes, without any distinct limits, into the anterior and 

 posterior edges. Both extremities are rounded, but the an- 

 terior one is considerably wider than the posterior. 



Seen from above or beneath (fig. 2), the shell exhibits a 

 rather regular, rounded oval form, with the greatest width 

 about equalling ^U of the length and occurring in the middle, 

 both extremities being obtusely pointed. 



The valves are perfectly equal, not very firm in con- 

 sistency, but connected dorsally by a sort of imperfect hinge, 

 extending from the most prominent part of the shell, and 

 terminating near its posterior extremity. In the region of 

 this hinge the dorsal face appears slightly grooved. The 

 outer face of the valves is evenly convex and perfectly smooth, 

 without any trace of lines of growth. In their upper part, 

 in front, the insertion for the adductor muscle of the shell is 

 easily observable (see fig. 1), and behind it the shell-gland 

 may likewise be plainly traced as an oblong oval area extend- 

 ing obliquely down the sides. 



The enclosed animal (see fig. 3) is rather voluminous, 

 and more generally its anterior part together with the antennæ 

 is found to be thrown out beyond the anterior edges of the 

 valves (see also fig. 1). By a strong curvature it admits, 

 however, of being completely withdrawn into the cavity of 

 the shell, in which case the edges of the valves close perfectly 

 all round. As in the 2 preceding genera, the animal is 

 attached to the shell by a dorsal ligament and by the adductor 

 muscle, being otherwise freely suspended in its cavity. The 

 division extending in front of this attachment is fully as large 

 as that lying behind it, though only consisting of the cervical 

 segment and the head. These 2 parts are defined dorsally by 



