Autodetus dud V 'ar amorphic Shells. — Clarke, 
329 
.Figs. 1, '-'. Umbilical and lateral 
views of Autodetus lindstrcemi, show- 
ing the apical cicatrix and the sinis- 
tral volution, xii. Hamilton shales: 
Hamburgh. N. Y. 
the width of the body-whorl. The attached surface is thick- 
ened or irregularly wrinkled, 
bearing some trace of the exter- 
nal markings of the host, which 
in every case where the support- 
ing surface has been retained, 
proves to be a brachiopod shell. 
The early whorls of the tube 
which are involved in the shell 
substance are not visible on this cicatrix, as they are in some 
other attached annelids, e. g.. Spirorbis, but this is undoubt- 
edly due to the thickening of the shell about its support. It 
is probable that young shells, if they could be detached, 
would show these sutures. Lindstrbm has observed the ten- 
dency of the basal or apical portion of the shell substance to 
spread laterally, or even to form short radiciform extensions, 
as in some of the corals (Omphyma), the attached pelecypods 
(Hippurites), and brachiopods (Richthofenia). This latter 
structure has not been observed in our species, though the 
thickening and spreading of the shell at the cicatrix is always 
noticeable. In a longitudinal median section of the shell, as 
shown in the accompanying figure of A. lindstrosm.i, we find 
evidence of a very considerable 
thickness of the walls of the sin- 
istrally coiled tube, and this 
thickness is palpably greater 
about the earlier whorls. There 
is also a certain looseness or cel- 
lular character in the shell sub- 
stance, noticeable wherever the 
deposit is greatest, as at the 
edges of the cicatrix, at the periphery of the body- whorl, and 
especially between the whorls and the solid columella, where 
there are considerable cavities, crossed by distant and 
delicate lamella?. In figure (i. which is an upper or umbilical 
view of a larger specimen of the same species, from which the 
interior portion of the last volution has been broken, the 
thickness of the outer wall is exposed and this appears to be 
more or less cavernous. This loose texture or cellular struc- 
ture is quite in accord with that of all attached annelidaii 
Fig, 3. A longitudinal median Mo- 
tion «>f Autodetus i i mtst re hi i. x'i. 
