- 250 - 



3P01IDYI.US GOOKII n. sp. 



Description .- '^hell of raedixim size, pectiniform, sutorbicu- 



lar, subequilateral, conspicuouslj? aurioulate for the genus ; rifrht 

 vilve decide dlj' inflated in the umbonal reg-ion; e::terior surface 

 sculptured v/ith five to seven primary radial ribs, in the form of 

 very broad, lov/, anrnlar, nriniary radials occupying the entire 

 area of the shell and separated by longitiidinal depressions, or 

 only their crests elevated as distinct ribs; the crests of the 

 primaries bearir^g- stout, blmit spines at irreg -lar and widely s->iac- 

 ed intervals; on the gently sloping sides of the primaries or on 

 the flat areas that 'vvoTold for-^i the sides of the primaries if they 

 ¥;ere elevate^!, appear secondaries, of irregular width, faintly 

 striate T longitudirially aad faintly scabrous, with exceedingly fine 

 scales arranged in very narrov;-, longitudinal series; auricles S'^arp- 

 ly differentiated from the dislr, subeoual, slip-htly rou?rhened or 

 scabrous; concentric sculpture represented only by fsint lines on 

 the auricles; left valve only moderately uniformly convex; primary 

 ribs never as bro'd as on the right valve, spinose, as on the Tl^-h't; 

 secondaries more prominent and more sharply sculptured, occasion- 

 ally bearing very short spines; inner margin of the valves irregii- 

 larly crenulated; interior of ri^bt valve with inconspicuous broad, 

 undulations corresp -ending to the external intercostal depressions. 

 Dimensions.- Right valve: lat. 24.6 mri. ; alt., 24.7 mm,.; 



