( 14 ) 



3. Pectunculus. Lam. M. 



Orbicular, almost len- Hinge arched, with Ligament exterior. (1) 



ticular, equivalved, sub- numerous serial oblique 



equilateral, close: beaks teeth, the middle ob- 



apart, with an area for the scure or none, 

 ligament. Fig. 45. 



at. Furrows longitudinal, distant, with fine striae, either longitudinal or 

 transverse. 



jS. Furrows longitudinal, projecting and radiating, with or without trans- 

 verse striae. 



4. Nucula. Lam. M. 



Oval, trigonal or ob- Hinge in a broken Ligament marginal, 

 long, equivalved, inequi- line, multi-dentated, in- partly interior, inserted 

 lateral ; beaks contiguous, terrupted in the middle in the hollow or spoon, 

 without an area. Fig. 46. by a hollow or a lit- (2) 



tie oblique projecting 

 spoon ; teeth often ad- 

 vancing and pectini- 

 form . 



(1) Several species become very thick with age, and frequently change their 

 form, which makes them difficult to recognise ; they are generally found in mud. 

 Foss. in London Clay, Woolwich Loam and Green Sand ; at Grignon, Courlagnon, 

 Beauvais, Bourdeaux, Dax, Piedmont, Sienna, Cassel, Ponicharirain, Soueurs, Plai- 

 sance, Mans } Touraine. 



(2) Foss. in London Clay, Crag Marl, Chalk Marl, at Grignon, Courtagnon, Parties, 

 Bourdeaux, Bourgogne, Plaisance, Mont-Marius* 



