482 FISSURELLID^.. 



This magnificent species, the Largest recent Emarginula 

 at present known to us, has, until very lately, been solely 

 observed in a fossil state. 



It is white both within and without, rather solid and 

 strong when adult, almost opaque, and of a more or less 

 conical figure. The sides are slightl}' compressed, the 

 front dorsal outline is moderately arcuated ; the hinder 

 dorsal outline is concave above, straightish below, and by no 

 means abruptly sloping. The base is elliptical, or oboval, 

 nearly equally rounded at both extremities, and mode- 

 rately convex at the sides ; the broader it is, the more 

 arcuated are the side-margins, and the less elevated, and 

 the less compressed is the shell. The vertex is acute and 

 recurved, but not so posterior as in most of this genus ; in 

 the younger shells it is situated at about two-thirds the 

 distance from the anterior extremity, in the adult it is 

 very much more central. The slit which is of equal 

 breadth throughout, and rather broad in proportion to its 

 length, extends but a little space from the margin, being 

 in general as three to fourteen ; its proportion to the length 

 of the base is very small ; its previous course is indicated, 

 as usual, by arcuated concentric striae. The sculpture is on 

 a small scale for the size of the specimens, and consists of 

 an immense number of slightly elevated radiating strife, 

 generally grouped by threes and fours, upon the larger ex- 

 amples, in the form of depressed costellee, that as well as the 

 very narrow interstices are decussated, and rendered slightly 

 granose, by very crowded coarse wavy concentric wrinkles. 

 The peculiarly close and depressed nature of this decussa- 

 tion is remarkable ; the hollows between the intersection 

 are extremely small and shallow ; indeed, towards the base, 

 where the interstices (always small) become more and more 

 diminished in size by finer intermediate radiating striae, and 



