In the numerous family of Lituolidæ the abode of the animal consists of a cement mixed with very fine particles of sand with larger ones imbedded in the surface. The order includes a wide range of forms divided into three genera, the simplest of which consists of a cylindrical tube twisted into a spiral gradually increasing in diameter, and attached to a foreign substance by one of its surfaces. The creature which lives in it is a uniform cord of sarcode, which sends its pseudopodia out through a large aperture at the extremity of its tube in search of food. Although the tube consists of sand imbedded in an ochreous-coloured cement secreted by the animal, its surface is smooth as a plastered wall. The spiral tubes of this genus take various forms, and in some cases are divided into chambers. The members of the genus Lituola exude from their surfaces a thick coat of cement with a quantity of siliceous particles roughly imbedded in it, but in some instances the particles are so uniform in size and shape, and are so methodically arranged, that the surface resembles a tesselated pavement. The usual form of the Lituola is a mere string of oval convex chambers increasing gradually in size, and fixed to shells and corals by their flat surfaces. In some instances the shells, or rather the substitutes for shells, take a nautiloid form, and become detached from the foreign bodies to which they were attached. In the highest forms of this genus the chambers are divided by secondary partitions. The typical form of the genus Valvulina is a three-whorled, three-sided pyramidal shell, with three chambers in every turn of the spire. The aperture is large and round, with a valve of smaller size attached by a tooth of shell to its rim. The creature itself has an exceedingly thin perforated vitreous shell, covered by an incrustation of calcareous particles, which so entirely blocks up the perforations that it can only extend its pseudopodia through the mouth of its shell. _Order of Vitreous Foraminifera._