NOTES ON THE COMMENSALS FOUND IN 
THE TUBES OF CHZETOPTERUS 
PERGAMENTACEUS. 
H. E. ENDERS. 
Waie I was collecting Chetopterus pergamentaceus during 
the past summer on the shoals about Beaufort,! North Carolina, 
I became interested in the commensals which occur with this 
annelid, and their number and variety led me to study their 
habits. 
These annelids, which grow in broadly U-shaped parchment 
tubes, are imbedded in diatomaceous, sandy shoals with from two 
to five centimeters of their free slender ends (about seven milli- 
meters or less in diameter) protruding above the sand flats at or 
below low-tide level. These tubes serve as convenient temporary 
shelters for several species of small animals, and as the perma- 
nent abodes of others. 
Of ninety-nine tubes collected and opened eleven were found 
without commensals while the remaining eighty-eight enclosed 
two annelids of the genus Nereis also one hundred and seventy- 
six crabs of the species? Polyonyx macrocheles (formerly Porce//- 
ana macruneles), Pinnixa chetopterana, Pinnotheres maculatus, 
and one species of. “stone crab," Menippe? Polyonyx and 
Pinnixa are found either singly or together in the same tube, but 
usually in pairs, male and female, of a single species. Among 
the number of tubes collected seventy-five enclosed Polyonyx in 
pairs or singly (total 143) ; fifteen enclosed Pinnixa; two, Pin- 
notheres, and one, a “stone crab," Menippe, while two serpulids, 
1] am indebted to the Hon. Geo. M. Bowers, U. S. Commissioner of Fish and 
Fisheries, for the privilege of occupying a table in the F isheries labøratory at 
Beaufort, N. C., and to Dr. Caswell Grave, the director, for courtesies shown. 
2I am also indebted to Miss Mary J. Rathbun, of the U. S. National Museum, 
for the identification of the species of crabs. 
3 The specimen was mislaid or lost at Beaufort, N. C. 
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