436 Mr STARK on Two Species of Pholas 



a tubular form, open at both extremities, like that of the Solen 

 or Mya *. From the superior opening of this tubular mantle 

 two united syphons arise, of which the anterior is the largest. 

 They are slightly dentated on the margin, and serve, the one for 

 the entrance of food, and the other for discharge. When cover- 

 ed by the tide, or in a basin, these tubes may be seen constant- 

 ly sucking in and ejecting the water. The foot is short and co- 

 nical, and, from its capacity of being projected and drawn in 

 within its circular covering, probably affixes itself by suction to 

 the bottom of the hole, and serves as a fulcrum for the rotatory 

 motion of the valves, or even may itself assist in deepening the 

 cell of the animal. Mr GRAY, in the third number of the Zoo- 

 logical Journal, has given some anatomical details regarding the 

 structure of the Pholades, particularly with regard to the singu- 

 lar falciform projections in the interior of the shell, which he 

 shews are nowise connected with the arrangement of the hinge ; 

 and POLI, in his " superb work " on the Testacea of the Two Si- 

 cilies, is said to have given the anatomy of the Pholas in de- 

 tail f- 



* There are several striking points of similarity of habit between the Pholades and 

 the Myae. The Myae burrow in sand, gravel, or clay, and project their tube to the 

 surface in the same manner as the Pholades. The form of their syphon is nearly the 

 same, as is also the mantle which connects the two valves. Their mode of sucking in 

 the water, and expelling it in jets, is the same in both. I have kept the Mya arena- 

 ria alive in sea-water for several days, and witnessed repeatedly its wetting the room 

 to a considerable distance, from its often repeated and violent ejection of the water. 

 The Myae ? however, at least the M. arenaria and truncata, though they easily pene- 

 trate soft clay or sand, do not seem to have the power of boring into hard substances ; 

 for in many specimens I have met with, in gravelly places, the shell was distorted, 

 from being placed between stones, which its force could neither remove nor form to 

 the contour of its shell. 



f- Since the foregoing remarks were written, I have seen POLI'S magnificent work, 

 and feel gratified by finding that the observations I have hazarded entirely coincide 



