170 PHILOSOPHICAL TRANSACTIONS. ["ANNOI697. 



Basil edition of 1565, is very ill drawn ; but being corrected according tothe 

 true meaning of the Cardinal's own words, it evidently represents the modern 

 cycloid. From hence it is manifest, that this curve was not first taken into 

 consideration either by Mersenne or Galileo, but some ages before ; though it 

 was not well understood before the then present time. 



The Dissection of the Scallop. By Dr. Martin Lister, F.R.S. N° 22Q, p. 567, 



Translated from the Latin. 



Dr. Lister observed that the hinge was slightly incurvated from the hollow 

 valve or shell, and carried over the other or flat valve, in such a manner as to 

 be firmly connected with both by a lateral cartilage ; also that another very strong 

 and black, cartilage was placed in the middle part of the hinge ; hence the won- 

 derful power of constriction possessed by the animal, as well as perhaps of 

 moving the flat valve somewhat in the manner of an oar, and of springing or 

 leaping, which property the ancients have often mentioned as peculiar to this 

 shell-fish. On laying open the shells he observed the following particulars, viz. 

 towards the right, and under the hinge, lies the hooded mouth, as in the 

 oyster ; the coverings of the mouth are formed by the meetings of the exterior 

 branchiae, or gills, which are muscular, and surround the whole animal from 

 the head to the opening of the vent, running from the region of the mouth to 

 the left. Of these exterior branchiae, that which lies on the flat shell adheres 

 by its upper centre to the border of a very large round muscle, which is inserted 

 at right angles into the middle of the shells ; in like manner is connected the 

 other exterior branchiae to the other head of the same central muscle. Both 

 these exterior or spurious branchiae consist of a very fine and pellucid membrane, 

 and being expanded or dilated towards the middle of the shells, adhere slightly 

 to them, so as not to be moved from their situation, and guard the animal's 

 back from any injury from water received into the shells ; from this place of 

 adhesion a thick and extraordinary muscle, like a kind of border, commences ; 

 it is represented in its state of contraction, but in the living animal it is won- 

 derfully extensile, even a great way beyond the edge of the shells, and is formed 

 into segments, and variegated with most elegant rufous lines : this part evidently 

 moved many days after being taken ; its use I conceive to be that of hulding, 

 as in a net, whatever is caught by it, when both the branchiated muscles are 

 stretched out beyond the shells in order to obtain food ; and the laciniae or mar- 

 ginal divisions serve to separate or drain off" the sea-water, while the food is 

 retained. This border may serve not only for catching the prey as in a net, 

 when extended beyond the shells, but even for killing any small animal or fish 

 by strong pressure, and also by its undulating-power, which is very remarkable. 



