Prof. Garwood — Calcareous Algce. 443 



ccenencliyma or interstitial tissue is present. The tubes are thin- 

 walled, irregular in form, often with undulated or wrinkled walls, 

 Avithout mural pores, and furnished with more or fewer transverse 

 partitions or tabulte " } 



At that time Nicholson still considered Solenopora as representing 

 a curious extinct hydrozoon, though already, in 1885, Nicholson and 

 Etheridge had discussed its possible relationship to the Calcareous 

 Algse. They did not, however, consider that there was sufficient 

 evidence for concluding that the true structure of Solenopora was 

 cellular, but added: " If evidence can be obtained proving decisively 

 the existence of a cellular structure in Solenopora, then the reference 

 of the genus to Calcareous Algse would follow as a matter of course." ^ 



In 1894 Dr. A. Brown ^ investigated more fully the material which 

 had been placed in his hands by Professor Nicholson, and gave an 

 account of all the forms referable to Solenopora known at that date._ 



To those already recorded he added descriptions of four new species 

 from the .Ordovician rocks — namely, S. Uthothamnioides, S. fusiformis, 

 S. nigra, and S. dendriformis, the two latter being from the Ordo- 

 vician rocks of Esthonia. 



In the same paper also he published for the first time a description 

 of a new species of Solenopora from the Jurassic rocks of Britain, to 

 which Nicholson, in manuscript, had already assigned the name of 

 S.jurassica, though, as will be pointed out later, it is probable that 

 two distinct forms were included by Brown under this name. 



This record of Solenopora from the Lower Oolites of Britain extended 

 the known range of this genus, for the first time, well into the 

 Jurassic period. In this paper Brown first brought forward good 

 evidence for removing Solenopora from the animal kingdom, and 

 placing it among the Coralline Algae, and Professor Seward, in vol. i 

 of his work on Fossil Plants, considers that there are good reasons for 

 accepting this conclusion. 



At the time of the publication of Dr. Brown's paper, and for some 

 years afterwards, the only formations in which Solenopora was known 

 to occur were the Upper Ordovician and the Lower Oolites. The 

 diversity of forms, however, met with in the Ordovician rocks, and 

 their widespread ' distribution, pointed to the probability of the 

 existence of an ancestral form in the older rocks, while it also 

 appeared incredible that no specimens of intervening forms should 

 have been preserved in the rocks representing the great time-gap 

 between the Ordovician and Jurassic formations. 



In this connexion Professor Seward remarks*: " It is reasonable 

 to prophesy that further researches into the structure of ancient 

 limestones will considerably extend our knowledge of the geological 

 and botanical history of the Corallinacese." This prophecy has been 

 ampljr fulfilled, especially as regards this particular genus, and recent 

 discoveries go far towards filling the previously existing gaps in our 

 knowledge of the vertical distribution of this interesting genus. 



1 Geol. Mag., Dec. Ill, Vol. V, p. 19, 



2 Geol. Mag., Dec. Ill, Vol. II, p. 534, 1885. 



3 Geol. Mag., Dec. IV, Vol. I, pp. 145 and 195, 1894. 

 ^ Fossil Plants, vol. i, p. 190, 1898. 



