14'J ISCIIN.X mi'.N IIAI.HI.I.I.A. 



the middle. <;irdlc having very small, solid, >mooth scales. Gills 

 almost ambient. ( < 'pr.) 



Lenirth 40, breadth i>ii mill.: divergence 135. 



Sitka to Pug^t Sound, 9-18 fms. 



Tr.H'hwI.nnn,, tni',,ln. OR., Suppl. Kep. B. A. 1863, p. l>4'. ; 

 Proc. Acad. Nat. Sci. Phila. 1865, p. 60. Ischnoradsia trifida CPR., 

 .!/>.. and PXI.I., I'roc. U. S. Nat. Mus. 1878, p. 881. 



I have not seen this species. The figure is from a rude sketch in 

 Carpenter's MS. Dr. Dall writes of it as follows: 



This rare and fine species is not particularly handsome, being of 

 dull and livid colors, but is peculiarly characterized by the straight 

 transverse ribs on the dorsal areas with spongy interspaces, and by 

 the pretty regular division of the lateral areas into three well 

 marked radiating costa?, which are separated in the insertion plate 

 by two fissures. No other species of the region resembles this in 

 srulptuiv. Mu/x.le with a pectinated margin in front produced into 

 rounded lappets at the corners. Gill rows as long as the foot, con- 

 taining each 28-35 branchiae. Veil absent. Mantle edge plain, 

 narrow. There is a small spherical lump on each side of the girdle 

 just behind the posterior ends of the gill-rows, which are turned out 

 toward the girdle and widely separated behind. The anus is large 

 median, and crenate, opening on the upper part of the hinder end of 

 the foot. No ovarian openings could be detected, and the species 

 presents some peculiarities which call for further research with more 

 material. (Dall.) 



1. KKCJULARIS Carpenter. PL 18, figs. 41-46. 



Shell oblong, elevated, dorsally carinated, the side slopes straight. 

 Surface appearing almost smooth to the naked eye. Color a uni- 

 form olive or slaty-blue, the girdle having more or less of a blue or 

 purple " bloom." 



The lateral areas are very little raised, and are sculptured with 

 numerous delicate radiating threads, occasionally branching toward 

 the lower margin, and freely branching along the posterior edge of the 

 valve. The terminal valves have similar delicate radii. The central 

 areas have numerous longitudinal, somewhat beaded threads, 

 separated by flat intervals. The posterior valve is elevated, with 

 anterior umlo. 



The interior is light blue. Sutural plates low, connected across 

 the HMIIS by a narrow plate which is silicate above and cut into 



