94 PROCEEDINGS OF THE ACADEMY OP 1879. 



pi. 3). Besides the color the form clearly differs in the very weak 

 serrulation of the median teeth. 



Dendronotus Dalli, Bergh, n. sp. Plate I. f. 21 ; PI. II. f. 9-12 ; PI. III. fig. 2-6. 



Animal ? 



Dentes mediani margine laevigata. 



Hab. Fretum Beringianum. 



In dredging on rocky bottom at a depth of thirty-five fathoms 

 in the Arctic Ocean, Bering Strait, August, 1855, Dr. Win. 

 Stimpson obtained the bulbus pharyngeus of a mollusk, which 

 proves to be a Dendronotus. 



The size of the bulbus was uncommonly large, the length being 

 about 10.5, the breadth 7.0, and the height about 6.0 mm. Its 

 form and that of the mandibles (fig. 2-4) resembled that of the 

 same parts in D. arborescens and D. purpureas, but of somewhat 

 darker color, the edge of the cutting blade (fig. 2c, 3c, 4) differ- 

 ing a little from that of the other species, and the serrulation of 

 the denticles being more distinct than in them. The tongue (PI. 

 II. fig. 9, 10) as in the other species. There were on the rhaehis 

 twemVy-four rows of teeth, in the sheath twenty-five developed and 

 two not quite developed rows, the total number of rows amounting 

 to fifty-one. The median teeth were of very dark, nearly black- 

 brown color, reaching a breadth of 0.3 mm., without any trace 

 of serrulation of the margin (fig. 11, 126). The lateral teeth 

 (fig. 5) number fourteen, rarely fifteen, quite as in the other spe- 

 cies, the four to five outermost also without denticulations (fig. 

 21a, fig. 5a). 



The bulbus clearly belonged to a Dendronotus different from the 

 two former species. The Dendron. arborescens has the cutting 

 edge of the median teeth very distinctly serrulated, and to the 

 very point of the teetli ; this serrulation is much weaker in the D. 

 purpureus and shorter, but it disappears entirely in the D. Dalli, 

 which, moreover, is distinguished by a somewhat peculiar form of 

 the cutting edge of the mandibles. As the length of the bulbus 

 pharyngeus in specimens of D. arborescens, preserved in spirits, 

 commonly is about one-tenth of the length of the whole body (cf. 

 my former paper) the D. Dalli is likely to reach the very notable 

 length of about 100.0 mm. 



* 



