CHAETODERMA BACILLUM. 201 



distal, glandular products of the cells have become dislodged. Passing through 

 the union of the pro- and metathorax (Plate 9, fig. 18) the epithelial lining 

 becomes thicker. In the anterior end of the metathorax it again grows thin 

 (Plate 9, fig. 16) save in the immediate neighborhood of the dorsal aorta, and 

 where folds appear, especially on the ventral side, the cement substance between 

 the cells assumes the form of minute granules (Plate 10, fig. 7). Intercellular 

 bridges may exist, judging from certain cells, but the state of preservation of 

 the material renders this uncertain. 



The liver, gonad, and intestine arise at practically the same level in the 

 posterior end of the metathorax (Plate 10, fig. 4), and are of typical structure 

 and arrangement. The latter statement is Ukewise true of the entire intestine 

 and of its outlet into the cloacal chamber. 



A careful examination has been made of the nervous and circulatory sys- 

 tems, but the results do not call for a description beyond that afforded by the 

 figures. The single specimen sectioned was a male with mature sex products 

 in the gland itself and to a sUght extent in the pericardial cavity. 



The cloacal chamber may Ukewise be passed with a few words only. Gen- 

 erally speaking the epithelial lining is composed of low cubical cells that become 

 somewhat more elongated in the neighborhood of the external openings of the 

 coelomoducts. There are, however, no extended patches of columnar epi- 

 thelium in this region such as occur in Chaetoderma nitidulum for example. 

 Each branchia is provided with 11-12 plates so far as can be determined from 

 cross sections. 



The coelomoducts communicate with the pericardial chamber by clearly 

 defined ciUated openings in the customary position beside the strong dorsal 

 commissure. Extending anteriorly each canal rapidly loses its ciliated coat, 

 assumes the characteristic glandular appearance and extends anteriorly about 

 one third the entire length of the ventral section with which it then unites. 

 The ventral division is provided with comparatively simple walls, the greatest 

 outpouching occurring at the level of the pericardial openings. The external 

 pores (Plate 10, fig. 3) are located in the usual position in the cloacal cavity. 



Chaetodertaa bacillum, sp. nov. 



Three specimens (one mutilated) of this species were dredged in 906 fath- 

 oms in the neighborhood of 200 miles southeast of Cape Cod, Massachusetts 

 (Sta. 2076A). All were silvery gray in color with a slight tinge of buff due to 

 the underlying somatic musculature, and are further characterized by a bright 



