70 The American Geoloqisz All^'nst, 1S96 
All att('iii[)t to coinpiire the basal appendagps to suckers, 
such as various gastropods use for purposes of attachment, 
would lead to the further assumption that their interior was 
filled with muscular tissue, and consequently connected with 
the circulatory system of the living animal. The writer was 
unable to study this question on account of the negative re- 
sults which followed his attempts to isolate the appendages; 
neither did he succeed in tracing the confluent canals, indi- 
cated b^^ the cross of pyrite at the apex of the shell, which 
may have effected a connection with the interior of the pyra- 
mid and thereby have become instrumental in producing a 
vacuum by the withdrawal of a fluid, similarto that found in 
the pedicels of the echinoids. The writer, however, is inclined 
to suppose that there existed no connection whatevei' between 
the interiors of the pyramid and of the appendage, but that 
attachment was eifected by the elasticity of the latter alone, 
especially by that of the central cup. The organ might then 
be compared to the chitinous suckers with which the males of 
certain water-beetles (e. g., Eunectes) are provided, and 
which possess no muscular tissue whatever but adhere to for- 
eign bodies by external pressure and by subsequently resum- 
ing the f)riginal shape through their own elasticity, thus 
producing a vacuum much like the India rubber plates which 
are used to fasten objects to the glass plates of show windows. 
The shape of the central cuj) as well as the fact that the ap- 
pendage consists of a substance which certainly was elastic, 
could be adduced in favor of this supposition, w^hile there 
seems to be no serious obstacle in the way of assuming that 
the animal, — which no doubt had a certain power of free 
moving. — had the further power of pressing the apex of the 
shell and with it the securely fastened cup to the body it 
washed to adhere to. 
The diagrammatic section, tig. '11, is intended to illustrate 
the working of the apparatus, the dotted part representing 
the latter in the state of compression preparatory to attach- 
ment, and the striated part shows the same in the state of 
attachment by suction. 
It should be remembered that however erroneous the at- 
tempt to explain the special operation of this organ may be, 
this does not alfect the fact that the attacliment was evidently 
only a temporary one and that the inijiressions left by the 
