OP CEETACEOrS PLANTS. 237 



This getiiis, which shows such similarity to the living Hali- 

 meda, is of special interest because previous to its recognition 

 no member of the Codiacese had been determined on the basis 

 of its structure, prior to the Tertiar}-. 



Boueina Hochstetteri, Toula. 



1884. Boueina JJochstettm, Toula, Sitzb. k. Akad. Wiss. Wien, 

 math.-imturwiss. 01., vol. 88, pp. 1319-1324, pis. vii-ix. 



1901. Boueina Sochstetteri, Steinmann, Bericlit. naturf. Ges. 

 Freiburg, vol. 11, pp. 1-6, text-figs. 1-7. 



In this alga the simple, Tiubranched body of the calcareous 

 thallus is 10-20 mm. long, 2-3-5 mm. thick, and is penetrated 

 by a system of branching canals which are connected without 

 any visible segmentation. The cross-section is circular or oval, 

 and in the central region the little branched canals of the axis 

 run more or less nearly parallel, in the periphery they are very 

 much smaller and stand at right angles to the surface and are 

 very freely diehotomously branched. The ultimate branches 

 are arranged very close together and form a kind of cortical 

 zone. In large specimens the central canal-sj-stem is replaced 

 by a simple cavity. Between the canals is an undifferentiated 

 calcareous skeleton. 



HoEizoiir. — Upper Neocomian. 



LooALTir. — Servia. 



The general habitat of this Neocomian member of the 

 Codiaceae appears to have been similar to that of the modern 

 HaUmeda. 



Steinmann's figures (Steinmann, 1901, text-figs. 2 and 3), 

 reproduced here as text-flg. 1, show the general character of the 

 cross-section of these algae and illustrate clearly the remarkable 

 likeness to the living Halimedri, a similar section of which is 

 shown in text-flg. 2. 



Fructifications for this fossil are not recorded, but this is a 

 point which tends further to strengthen its supposed affinity to 

 Ealimeda, for in the living genus the spores are not developed 

 on the parts already penetrated by calcareous matter. 



It may be remarked that though, as Steinmann points out, 

 there is a great similarity between the fossil and the living genus, 

 the parts compared are only the " stalk " region of the plants 

 and this is similar in several of the Codiaceae. 



