PECTEN. 



the flatter valve is a small notch for the passage of a 

 byssus: muscular impression large, placed rather on one 

 side; muscular impression of the mantle without any 

 sinus; hinge linear, ligament consi^^ting of three portions, 

 of which the two lateral are elongated and follow the 

 hinge line, the remaining p(»rtion triangular, thick, placed 

 in a central pit within the hinge. 



We have stated above, that immediately below one 

 ear of the flatter valve is a notch for the passage of the 

 byssus; we mention this again because we believe that 

 ail the Pectinidae are naturally attached by a byssus, 

 although it is seldom observeo, even in the living speci- 

 mens; we acrrount tor this circumstance, hovvever, by 

 supposing that their attachment by the byssus is very 

 slight; we have seen them attaching their threads by 

 means of their small and slender foot. Many of the 



• 



Pectines have a row of small sharp teeth on that side of 

 the shell under the ear, which forms a part of the sinus 

 for the byssus. 



The numerous species of which this genus is com- 

 posed may be divided nearly as follows: 



1. Both valves convex, equal or nearly in size, an 



examfde of which is given in our plates. 



2. One valve flat, the other deep or convex For 



an example of this see Fecten Jacoha?us. 

 - 3. Both valves rather convex, not meeting all round; 

 exanjple P. Pleuronectes 



4, Both valves convex, but unequal in size; ex- 



amples P. bifrons and aurantlacus. 



5. Irregular, apparently adherent by the outside, 



but only taking the form of whatever it is at- 

 tached to in consequence of being close pressed 

 to it. This hav« generally been thought to belong 

 to the Spondylitic, and has been named Hin- 

 nites by De France; we have, however, proved 

 it to be a Pecten: see Zool. Journal. Fecten. 

 Pusio is an example of it. 



In the singularity of their structure and in the beau- 

 ty of their colouring the Pectines yield to none of the 

 bivalves; among the handsomest and most remarkable, the 

 following are deserving of particular notice, viz. 



F. bifrons, for its brilliant purple colour within. 



