PULL ASTRA. 121 



usual thick fleshy linguiform foot, very moderately geniculated, 

 and capable of all the phases from obtuse to pointed; it is 

 pure white,, and has not the byssal groove of the tribe, which 

 is a considerable variation of structure, and the teeth are not 

 so slender, long, or parallel, more resembling those of Venus, 

 from which this animal scarcely differs. The mantle pos- 

 teriorly forms the siphons, which are soldered together three 

 parts of their length, becoming separated for the remaining 

 portion ; the colour is delicate pale lemon, tinged with red- 

 brown at the bifurcation ; they are of the same size, the 

 branchial being truncate at the extremity, and clothed with 

 fourteen pointed cirrhi, whereof seven are rather the largest, 

 marked at their bases on each side with a patch of bistre, the 

 interstitial ones are white ; the anal tube curves upwards as 

 in its congeners, and does not appear truncate, in consequence 

 of its edges being a little inflexed ; it has sixteen short white 

 cirrhi at the orifice, which has also around it a dirty red-brown 

 fine line ; the tubes, when frilly extended, are less long than in 

 the two preceding species ; they do not, as in Venus, measure 

 more than half the transverse measure of the shell. The pair 

 of subcircular branchiae on each side are pale drab, hung very 

 obliquely; the under ones are at least double the size of the 

 upper, and strongly marked by the transverse vessels of the 

 circulation; the palpi are subtriangular, short, and well striated. 

 The liver appears scanty and of a pale green. 



This species inhabits the coralline zone at Exmouth, but is 

 rarely taken alive ; dead shells in good condition are frequent. 

 We almost think that this species and its variety the P. Sar- 

 niensis should, from the absence of the byssal groove and the 

 greater divergence of the teeth from the type, be transferred 

 to the Veneres. The P. aurea has not occurred alive ; is it 

 distinct from the present species ? the teeth of the two are of 

 similar character, and if it is without the byssal groove, it 

 would appear that it ought to accompany the P. viryinea to 

 the typical Veneres. 



