PLACIPHORELLA. 309 



and the head expansion doubled up, but the hairs are very well 

 preserved. Over the whole of the marginal part are very short 

 crowded deciduous whitish hairs. Over the greater portion of the 

 surface are scattered distant large tubular, horny hairs, which seem 

 to arise deep in the girdle. These hairs are not scaly as in P. blain- 

 villii, but present when perfect the aspect of Aspergillum vaginiferum 

 in miniature. I cannot say with confidence that all the hairs are 

 so sculptured, for some which look perfect do not show it. " 



A. sketch made by Dr. Carpenter from a hair of this specimen is 

 copied on pi. 62, fig. 86. The hairs on Gould's type are broken to 

 Tery short stumps, not long enough to show their structure. 



P. BOREALIS Pilsbry, n. sp. PI. 66, figs. 14, 15, 16, 17. 



Shell similar in general characters to P. velata. Brown at the 

 sides, light along the middle. Surface dull, showing growth- 

 lines. 



Valves not beaked, having a slight forward bend in the middle 

 at the sinus, but not " false beaked " there as P. velata is. Lateral 

 areas more strongly 2 ribbed. Anterior valve sculptured with numer- 

 ous very low, wide radiating riblets. Posterior valve having the 

 mucro near the posterior margin, depressed, the slope in front of it 

 rising, convex rather than concave ; posterior margin waved 

 inward. 



Interior light blue-green. Sutural plates separated in all the 

 valves by an angular, spongy sinus. Anterior valve having 11 slits, 

 the teeth unequal, lobed or. roughened. Median valves having one 

 slit, the teeth being peculiarly curved outward at its edges. Posterior 

 valve much less callous inside than that of P. velata, the insertion- 

 plate uneven, roughened, but having a single well developed slit on 

 each side; the median tail-notch deep and wide. Eaves very 

 spongy. Girdle unknown to me. 



Breadth of anterior valve 16, length of front slope, including 

 teeth 4i mill. 



Breadth of a median valve 22, length from sinus to beak 4 mill. 



Breadth of posterior valve 15, length direct from sinus to sinus 

 5 mill. 



Divergence 135. Measurements of breadth include the inser- 

 tion-plates. 



Bering Island, Bering Sea (Grebritzki). 



Placiphorella stimpsoni DALL, (part), Proc. U. S. Nat. Mus. 1886 



