24 GENERAL FEATtlRES, METHODS, ETC. 



tory mentioned in the introduction. However, it cannot be said that in any 

 case we have any very definite information regarding the geographical limits 

 or relative abundance of a single species. 



There is little to be said regarding the vertical distribution of the species 

 described in the present paper. Where several individuals have been secured 

 from a number of stations each species appears to be restricted to a fairly tlefinite 

 depth. Chadoderma nitidulum is reported to have a range of from 14-1250 

 meters. A much greater depth may be possible for C. hawaUensis from Station 

 4130 where the initial sounding recorded 13(i2 fms.; but since the closing sound- 

 ing was 358 fms. it is probable that the latter figure is more nearly correct, as a 

 second specimen was taken at a depth of 528 fathoms (Sta. 3992). In many 

 places the ocean floor is exceedingly rough and characterized by high almost 

 vertical cliffs bounding fissure-like valleys. Under such circumstances a num- 

 ber of soundings are desirable in order to avoid the necessitj' of accepting great 

 extremes in vertical distribution though these may in realitj' exist with certain 

 species. 



Mode of life, Food. — The species belonging to the Chaetodermatidae 

 are, so far as known, inhabitants of the sea bottom where they excavate burrows 

 which they rarely leave. Wiren {'92) who kept over one hundred specimens of 

 C. nitidulum in captivity says they progress through the ooze by means of the 

 alternate contraction and expansion of the prothorax aided by movements of 

 the entire body; and that when at rest they ordinarily direct the body vertically 

 with the cloacal chamber widely expanded, and the branchiae fully exposed at 

 the opening of the burrow at the surface. When disturbed they disappear 

 instantly several inches into the mud. In most respects these observations 

 answer for C. crudita which I kept some time in captivity. This animal from, 

 time to time advanced through the ooze in the manner described by AViren but 

 it never appeared at the surface. For hours together it remained quietly in its 

 burrow with the gills fully expanded and when disturbed retreated but slowly, 

 though the gills were at once retracted and the cloacal chamber closed. The 

 individuals acting in this manner were apparently in a normal condition since 

 the alimentarj' canal of several kejit in captivity for nearly one month contained 

 quantities of food. 



The members of the suborder Neomeniina, on the other hand, are not 

 known to burrow, but are usually found on some species of hydroid, coral, and 

 exceptionally (Proneomcnia vagaus, P. desiderata), on plants. Now and then 

 specimens have been dredged unattached and it may be that they, like Neomenia 



