62 ■ CHAETODERMA ARGENTEA. 



outline slightly in front of the radula (Plate 27). Throughout its entire course 

 to the hinder borders of the radula its walls, more than commonly muscular, 

 afford lodgment for numerous salivary glands whose secretion stains darkly 

 with haematoxylin . The radula, its supports and musculature are typically 

 situated but are exceptionally heavy and powerful. The remaining divisions 

 of the digestive tract are related as usual and are represented on Plate 27. 

 Countless thousands of diatoms, together with nondescript organic and inorganic 

 remains, fill the intestine and in some specimens, the stomach. 



The pericardium is a comparatively spacious chamber, extending backward 

 some distance over the cloa.cal cavity (Plate 27, fig. 9), and is perforated by the 

 superior gill retractors; but otherwise neither it nor the tubular heart and the 

 connecting sinuses are peculiar in any important particular. 



The nervous system has been studied in considerable detail, and in all 

 essential respects has been found to resemble that of C. attcnuala for example. 



The gonad, with the usual characters, opens into the pericardium by com- 

 paratively wide, dorso-ventrally compressed tubes. The inner openings of 

 the coelomoducts are likewise of large size (Plate 27, fig. 8) and the adjacent 

 ciliated section also though the latter is unusually short. This ciliated section 

 unites with a division of the glandular part (shown on the left, Plate 27, figs. 

 2, 8). The outlet (Plate 27, fig. 9) occvu's in the customary position and is sur- 

 rounded by the glandular modification of the cloacal epithelium as in C. atten- 

 uata and a few other species. 



Chaetoderma argentea, sp. nov. 



One specimen (Plate 4, fig. 7) of this species was taken in southern Alaska 

 in the green mud of Behm Canal (Sta. 4231) at a depth of 82-113 fathoms. It 

 was in a moribund condition and with the exception of slight movements of the 

 body and gills gave no signs of life. The measurements are, total length 24 mm. 

 diameter of the prothorax 1.6 mm. while the greatest diameter of the preabdomen 

 was 2.6 mm. The color in life and in a preserved state was a silvery white. 



The cuticle is scant in amount and the hypodermis is comparatively low 

 and is composed of small cells cubical or low columnar in form. Among these 

 are the giant cells (Reisenzellen) from which the secretion has disappeared but 

 they are attached to faintly staining fibres whose exact relations have not 

 been determined. The spines are represented (Plate 37, fig. 6). 



Although the animal when captured was alive it never relaxed sufficiently 

 to allow the buccal sensory plate to become exposed. In sections this last named 



