In 1878 Munier-Chalmas expressed the opinion, which was supported by strong evidence, that _Ovulites_ should be referred to the siphoneous algae[290]. He regarded it as generically identical with _Penicillus_ (_Coralliodendron_, Kützing). It has already been pointed out that in _Penicillus_ the apical tuft of filaments is partially calcareous (fig. 33, O)[291]. The individual calcareous segments agree almost exactly with the fossil _Ovulites_. As a rule the Ovulites occur as separate egg- or rod-like bodies, but Munier-Chalmas informs me that occasionally two or three have been found joined end to end in their natural position. The terminal holes in the fossil specimens represent the apertures left after the detachment of the calcareous segments from the uncalcified filaments of the alga. The segments with two holes at the broader end were no doubt situated at the base of dichotomising branches as shown in fig. 33, K. The restoration of _Ovulites_, shown in fig. 33, K, bears a striking resemblance to the figure of an Australian _Penicillus_ given by Harvey in his _Phycologia Australica_[292]. It is probable that these Eocene forms agreed closely in habit with the recent species of _Penicillus_. The portions preserved as fossils are segments of the filaments which probably formed a terminal brush of fine branches supported on a stem. The retention of the original generic name _Ovulites_ is on the whole better than the inclusion of the fossil species in the recent genus. The Tertiary species lived in warm seas of the Lower and Middle Eocene of England, Belgium, France and Italy. _Halimeda._ An example of an Eocene species of _Halimeda_ has been recorded by Fuchs from Greifenstein under the name of _Halimeda Saportae_[293]. The impression has the form of a branched plant consisting of wedge-shaped or oval segments, and there is a close resemblance to the thallus of a recent _Halimeda_, e.g. _H. gracilis_ Harv. It is not improbable that Fuchs’ determination is correct, but without more definite evidence than is afforded by a mere impression it is a little rash to make use of the recent generic name. γ. Dasycladaceae. In this family of Siphoneae are included a number of genera represented by species living in tropical and subtropical seas. The thallus consists of an elongated axial cell fixed to the substratum by basal rhizoids, and bearing whorls of lateral appendages of limited growth which may be either simple or branched. Many of the lateral branches bear sporangia or spores. The thallus is in many species encrusted with carbonate of lime. The two genera _Acetabularia_ and _Cymopolia_ may be briefly described as recent types which are represented by trustworthy fossil forms. [Illustration: FIG. 34. _Acetabularia mediterranea_ Lamx. From a specimen in the Cambridge Botanical Museum (nat. size).] _Acetabularia._ Figs. 33, I, and 34.