22 MICROPLAX. 



the sutural laminae, but DO slits at all are to be seen. The laminae 

 are very square, not wavy as in the other covered species. There 

 is a very slight indication of riblets or striae continuing from the 

 diagonal rib down to the edge of the lamina, but I cannot see the 

 least indication of nicks or lobes at the edge. The sutural laminae 

 are extremely slight, projecting over each other about to the line 

 of the mucro, with the very slightest sinus in the middle between 

 them. 



The front valve is horse-shoe shaped, with flat base, mucro a 

 little removed from the margin. It is nearly smooth at the mucro, 

 becoming gradually more granulose. The whole color is a greenish 

 pink. 



The intermediate valves all point forward ; their mucrones in no 

 case touch the posterior edges ; two smooth, diagonal ribs, curved 

 forwards, separate the lateral and central areas, both of which are 

 granulose. 



The posterior valve has the mucro a little anterior, the two 

 oblique ribs curving backwards. 



It will be noted that the umbo or mucro in the posterior valve is 

 directed forward, whilst in the other valves it is, as usual, directed 

 backwards. 



The divergence is 76, very elevated. The exposed part of the 

 valves measure about H X It mill. The girdle is everywhere 

 minutely granular too minutely to be shown in the illustration. 



