Josua Trimmer, Practical Geology and Mineralogy with Instructions for the Quality Analysis of Minerals, Londres, John W. Parker, 1841, p. 353.

A form of limestone also occurs, called indusial, from its containing immense numbers of the indusiae , or cases of the larvae of phryganeae, insects the living species of which may also be observed in our ponds, and which have the power of fixing small freshwater shells to the outside of their tubular cases. More than a hundred shells of a small species of Paludina have been counted on one tube of a large species of Phryanea, which abounds in the eocene lakes of Auvergne; and strata of indusial limestone, each six feet thick, which may be traced over a considerable area, are almost wholly composed of these tubes enveloped in travertin, so many as ten or twelve occurring in a cubic inch.