194 CORBULID.^. 



NEi^RA, Gray. 



Shell transversely ovato-pyriform, inequi valve, inequi- 

 lateral, more or less beaked and gaping posteriorly ; sur- 

 face smooth, or striated, or ribbed longitudinally, never 

 punctated, with or without an epidermis ; valves strength- 

 ened internally with a longitudinal rib ; hinge composed 

 of a cartilage-fulcrum, usually oblique and spathulate in 

 each valve, sometimes with a minute tooth beside it, and 

 a more or less developed lateral tooth on the rostral side 

 of one or both valves ; ligament external, small ; muscu- 

 lar impressions large ; pallial with a very shallow sinus. 



Animal oblong, mantle closed in front, except a plain- 

 edged orifice for the passage of a lanceolate foot ; siphons 

 short, united, unequal, the branchial largest, both bearing 

 a few long filiform cirrhi at their sides, extending beyond 

 the orifices ; anal siphon with a very extensile membranous 

 valve. 



When the only species of this genus hitherto figured as 

 British, was first made known, our conchologists were 

 inclined to question its indigonousness, and to regard it 

 as accidentally introduced. Yet now not only is the 

 Netera cuspidata extant in many British collections, but 

 two other species have been added to keep it company 

 within the last three years ; of those two, one until very 

 recently was known only in the fossil state, and both till 

 within the last three years were supposed to be peculiar to 

 the Mediterranean Sea. Such advances in our knowledoe 

 of a genus so little known to most collectors as Neetra 

 have been due entirely to the more active employment of 

 the dredge, and the greater energy and adventure of the 

 naturalists who have, with such excellent results, kept 



