94 



Genus 2. CUCULL^EA, Lamarck. 



Animal ; similar to that of Area. 



Shell ; rather inequilateral, trapeziform, ventricose ; hinge linear, 

 straight, narrow, very slightly toothed ; teeth at the extremities, 

 prolonged ; place of adhesion of the posterior muscle in each 

 valve chambered. 



This genus is founded upon a character which many conchologists think 

 is not worthy of causing a dismemberment of the species from those of 

 Area. In many species of Area the place of attachment of the posterior 

 muscle in each valve is bounded by a gentle ridge. In Cucullaa the ridge 

 is so far developed as to form a chamber ; and there is a general pecu- 

 liarity about the shell in all its details. The hinge is quite marginal, with 

 the teeth almost obsolete, yet at the extremities of the hiuge the teeth are 

 prolonged obliquely almost into ribs. Two species have been described, 

 inhabiting China, Nicobar, and the Mauritius, but it is more than probable 

 that they are varieties of the same, originally described by Martini. 



Species. 

 1. concamerata, Mart. 2. granulosa, Jonas. 



Figure. 



Cuculuea concamerata. PI. 34. Pig. 187. Shell, with the left valve 

 dropped to show the posterior chambered ridge and narrow linear 

 hinge. 



Genus 3. PECTUNCULUS, Lamarck. 



Animal ; orbicular, its mantle freely open with simple margins, 

 which are someivhat enlarged in the branchial and anal regions ; 

 foot large, semilunar, deeply grooved so as to form a disk with 

 undulated edges ; no byssus ; lips formed of a linear prolonga- 

 tion of the branchial lamince. (Forbes.J 



Shell ; orbicular, lenticular, equivalve, slightly inequilateral, mostly 

 covered with a hairy epidermis ; umboes but little separated 

 from each other, the intervening ligament area being small ; 

 teeth set in a curve, the middle ones being generally more or less 

 obsolete. 



