OF CONCHOLOGY. 103 



oblique lines of growth. Last whorl fiat above the carina and 

 rounded below it. The ridge below the carina becomes almost 

 as large as the latter, which is less prominent than upon the 

 upper whorls. Below the ridge alluded to are others gradually 

 diminishing in size anteriorly to the number of eight or ten, of 

 which onlv two or three are at all prominent. 



Lon. -84, lat. -36 in., defl. 80°. 



Habitat, North Harbor, Unga Island, in six fathoms, muddy 

 bottom, Dall, 1865. 



I take a melancholy pleasure in dedicating this beautiful 

 species to the memory of the lamented Robert Kennicott, first 

 Director of the Scientific Corps of the W. U. Tel, Expedition, 

 well known by his labors in the cause of science, and a martyr 

 to his devotion to them, in the field. It has a remote general 

 resemblance in miniature to the large Pleurotoma oxytropis, 

 Sby., from Panama, but is not closely allied to any species 

 known to me, or figured in the monographs. 



MARGINELLID.E. 



Pbrsicula dubiosa, n. s. 



Shell stout, solid, very thick and rather broad. Form less 

 attenuated than that of P. phri/c/cea, posteriorly ; shorter and 

 stouter than P. imbricata. Apex covered with a thin, even 

 layer of callus. Labium and labrum nearly parallel. Outer lip 

 moderately thickened, inner with a moderate deposit of white 

 callus. Outer lip nearly smooth, with a few faint grooves on 

 the internal margin near the posterior end. Inner lip with one 

 broad fold, grooved in the middle, two plicae above and one 

 (forming the posterior termination of the columella) below it. 

 Notch deep and oblique, a shallow sinus at the anterior ex- 

 tremity of the outer lip. Color lively yellow brown, with un- 

 certain fluctuating white bars, spots and streaks irregularly dis- 

 posed, with a general tendency to elongation in the direction of 

 the lines of growth. Callus above the spire marked with a circle 

 of radiating brown dots, with an obscure white band outside of 

 them ; a dark brown patch on the outer edge of the outer lip. 



Lon. '3 in., lat. '2 in. 



Habitat, Acapulco, Mexico. 



One specimen was obtained from half a bushel of fragments 

 and beach worn shells, purchased by me at Acapulco, in Octo- 

 ber, 1868. 



It is at once distinguished by its color and markings from any 

 other of the west coast species. The plications of the inner and 



