88 



BULLETIN 93^ UNITED STATES NATIONAL MUSEUM. 



Tlio labriim (fig. 17&) has about 12 teeth on each side of the notch. 

 Mandible as in B. ampTiitrite. Maxilla (fig. 17e), with six spines 

 between the upper and lower pairs. It is like some specimens of 

 B. amijTiitrite niveus, having the lower pair of large spines on a shght 

 projection. Tlie labral palpus (fig. 17 d) is like that of B. ampliitrite 

 niveus, in having an external row of long spines, but the opposite face 

 (not sho^vn in the figure) has a very serried band of short spines 

 directed toward the labrum, mstead of a single row, as in amiiihitrite. 



The first cirrus has rami of 19 and 14 segments, more miec^ual than 

 usual, the posterior ramus about three-fourths as long as the anterior. 

 Cirrus ii has slightly unequal rami of 12 and 10 segments. Cirrus iii 

 has 15, 14 segments, but the posterior ramus is but little more than 

 two-thirds as long as the anterior. The longer ramus has few long 

 spines on the lower 9 segments, but there are a few short ones on and 

 adjacent to the anterior margin (fig. 17/); also spines along the 

 posterior outline. The inner faces of these segments have very few 

 spines or none. The shorter ramus has armature like the longer on 

 the lower five segments, but their inner faces are densely covered 

 with long spines. The distal segments of both rami are densely 

 covered with long spines. Cin'us vi has five pairs of spines, with some 

 minute ones near their bases and along tlie posterior outhne. 



Another individual of the same lot has cirrus i with 18 and 12 

 segments, posterior ramus four-fifths tlie length of anterior. Cirrus ii, 

 11 segments on both rami, anterior ramus longer by two. CiiTus iii, 

 14 and 11 segments. The labrum (fig. 17a) has only five teeth on each 

 side, so that at first I thought it coidd not be improvisus; but as all 

 other characters are exactly hke the others of the same colony exam- 

 ined, I am reluctantly obliged to admit that what was thought to be 

 one of the most tangible differences between improvisus and ampJd- 

 trite is not a wholly reliable criterion, though it holds in all other 

 specimens I have dissected. 



Locality. 



South Downs 



Rochelle, Franc-e 



Station 2057, cast of Cape Cod (S6 fathoms) . 



Quinnipiac River, Mass 



Queen Anne County, Md., opposite Chester- 

 town. 



Chesapeake Beach, Va 



Sullivan's Island, S. C 



Winyah Bay, S. C, Station 1641-2 



Savannah River, Ga 



Jamaica 



Collector. 



Rev. Mr. Sheldon 



Jeffreys coll 



Albatross 



E. B.Wilson 



E. G. Vanatta 



Chas. S. Washington. 



Wm. G. Mazyck 



Fish Hawk (l-S^lSQl) 



J. S. Raymond 



C. B. Adams 



Notes. 



Jeffreys coll. PI. 24, figs. 3-36. 



On Solen. 



Young only; identification 



not positive. 

 On oyster shells. PI. 24, 



figs. b-bd. 

 Fresh-water stream; coll. A. 



N. S. P. 

 On wood. 

 Coll. A. N. S. P. 

 Bottom temperature 50° F. 

 On piles. 



