Rothpletz[281] instituted this genus for certain small spherical or oval bodies varying from 1 mm. to 2 cm. in diameter, which have been found on crinoid stems or shell fragments of Triassic age. Each spherical body consists of dichotomously branched single-celled filaments, between 50 and 100µ in breadth, and from 300–500µ in height. The tubular cavities occasionally swell out into spherical spaces which are regarded by Rothpletz as sporangia. There is not sufficient evidence that _Sphaerocodium Bornemanni_ Roth. has been correctly referred to the Codiaceae. The sporangia-like swellings described by the author of the species are not by any means conclusive as characters of important taxonomic value. Figure 37, D, illustrates the general structure of the fossil as seen in a transverse section of one of the calcareous grains. Like _Girvanella_, which has been referred by some writers to the Siphoneae, _Sphaerocodium_ occurs in the form of oolitic grains. In the Triassic Raibler and St Cassian beds of the Tyrol, as well as in rocks of Rhaetic age in the Eastern Alps, it makes up large masses of limestone. Rothpletz compares the structure of this genus with that of the recent alga _Codium adhaerens_ Ag., but it is wiser to regard such tubular structures as _Girvanella_, _Siphonema_[282] and _Sphaerocodium_ as closely allied organisms, which are probably algae, but too imperfectly known to be referred to any particular family. _Penicillus._ The recent genus _Penicillus_ is one of those algae formerly included among animals. Fig. 33, O, has been copied from a drawing of a species of _Penicillus_ given by Lamouroux[283] under the generic name of _Nesea_ in his treatise on the genera of Polyps published in 1821. He describes the genus as a brush-like Polyp with a simple stem. The thallus consists of a stout stem terminating in a brush-like tuft of fine dichotomously-branched filaments. The apical branches are divided by regular constrictions into short oval or rod-like segments which may be encrusted with carbonate of lime. A few of the segments from the terminal tuft of a recent _Penicillus_ are shown in fig. 35, E. Each of these calcareous segments has the form of an oval shell perforated at each end, and the wall is pierced by numerous fine canals. _Penicillus_ is represented by about 10 recent species, which with one exception live in tropical seas. The recognition of _Penicillus_, or a very similar type, in a fossil condition is due to Munier-Chalmas[284]. This keen observer has rendered great service to palaeobotany by directing attention to the calcareous algae in the Paris basin beds, and by proving that many of the fossils from these Tertiary deposits have been erroneously included by previous writers among the Foraminifera[285]. It is greatly to be desired that Prof. Munier-Chalmas may soon publish a monograph on the fossil Siphoneous forms of which he possesses a unique collection.