Calvin on- a new Ttibicolar Annelid. 25 
were small and inconspicuous, we might suppose that they had 
been overlooked, and that further examination would show 
them to be more generally distributed than we are at first in- 
clined to believe; but in place of being inconspicuous the tubes 
are not unfrequently a quarter of an inch in diameter and two 
inches in length. Moreover, unlike all other worm tubes of 
the group known to me, these are uniformly coiled in a long, 
loose, somewhat irregular spiral, and the successive brownish 
volutions stand out conspicuously on the freshly fractured sur- 
faces when the coral is broken in the right direction. It would 
probably be a better description of the actual state of affairs to 
speak of the tubes as twisted rather than coiled. The volutions 
while for the most part in contact, lack the regularity of the 
volutions of Loxonema^ Murchisonia or any of the long spired 
gasteropods, resemblance to which a first glance is likely to sug- 
gest. The irregularities about the sutures remind one of the ef- 
fect of torsion, and the tube diameter is not unfrequently di- 
minished between two contiguous volutions. All the irregular- 
ities and appearance of twisting, however, are due to peculiar- 
ities in the mode of growth and not to any agencies that have 
affected the tubes since they were formed. 
In all the specimens before me the spiral is sinistral. A sec- 
tion across the axis is circular or sub-circular. The surface is 
marked by transverse lines of growth that are ajDproximately 
parallel and horizontal throughout the whole length of the tube, 
any change in the direction of the successive parts of a given 
volution producing no change in the general parallelism of the 
lines of growth. It would seem as if the mouth of the tube had 
been always horizontal, quite regardless of the fact that the as- 
cending spiral axis during the growth of any simple volution 
was directed successively to ever}' point of the compass. The 
upward growth of the tube was effected by the addition of 
equal vertical increments all around the margin of the aperture, 
and yet, notwithstanding all this, the creature managed to coil 
around an imaginary vertical axis with surprising regularity. 
There arc no longitudinal markings of au}^ kind, except that 
very rarely there are faint grooves and ridges, evidently due to 
contact of the edges of the septa of the coral with the outer sur- 
face of the tube. The tube tapers very gradually, and the 
