Prof. Garwood — Calcareous Algce. 445 



the opinion that Girvanella might ultimately come to be regarded as 

 referable to the Siphon ese Yerticillatse. 



In 1898, however, this genus was still only doubtfully placed with, 

 the Calcareous Algae, for Seward, in his work on Fossil Plants,^ remarks: 

 " The nature of Girvanella, and still more its exact position in the 

 organic world, is quite uncertain. . . . We must be content for the 

 present to leave its precise nature still sul judice and, while regarding 

 it as probably an alga, we may venture to consider it more fittingly 

 discussed among the Schizophyta than elsewhere." 



In 1908, however, Eothpletz, in discussing the relationship of 

 Spherocodium and Girvanella, reaffirms his opinion that the latter 

 must be referred to the Codiacese.^ 



Mitcheldeania. 



This genus was first described by Mr. Edward Wethered from 

 the Lower Carboniferous beds of the Forest of Dean^ under the name 

 of Mitcheldeania Nicholsoni; it was referred by him to the Hydractinidse, 

 and considered to be allied to the Stromatoporoids. The figure 

 accompanying this paper unfortunately fails to show any of the 

 characters of the organism, but a better figure of the same species 

 was subsequently published in the Proceedings of the Cotteswold 

 Naturalists' Field Club.* 



In 1888 Professor H. A, Mcholson published in the Geological 

 Magazine * figures and descriptions of a new species of this genus 

 (Jf. gregaria), and redefined the genus as having " the form of small, 

 rounded or oval calcareous masses made up of capillary tubes of an 

 oval or circular shape, which radiate from a centi'al point or points, 

 and are intermixed with an interstitial tissue of very much more 

 minute branching tubuli ". He compares the larger tubes to zooidal 

 tubes, and states that they " communicate with one another by means 

 of large, irregularly-placed foramina resembling ' the mural pores ' 

 of the Favositidse, and they occasionally exhibit a few irregular 

 transverse partitions or tubulse ". 



With regard to the systematic position of this genus Nicholson 

 remarks: "In spite of the extreme minuteness of its tissues, the 

 genus Mitcheldeania may, I think, be referred with tolerable 

 certainty to the Coelenterata ... its closest affinities seem to 

 be with the Hydrocorallines ... on the other hand all the 

 known Hydrocorallines possess zooidal tubes which are enormously 

 larger than those of Mitcheldeania ; and tliere are other morphological 

 features in the latter genus which would preclude its being actually 

 placed, with our present knowledge, in the group of the Hydrocorallincey 



Since this description by Professor Mcholson no further account 

 of this organism, so far as I am aware, has been published, and its 

 reference to the Sydro%oa rests on Professor Nicholson's description. 



During the past few years I have collected a large amount of 

 material from both of the type localities from which Mr. Wethered 



^ Op. cit., vol. i, p. 125. 



2 Eothpletz, Kungl. Sven. Vets. Akad. Hardl., Bd. 43, No. 5, loo. eit., 1908. 



^ Geol. Mag., Dec. Ill, Vol. Ill, p. 535, 1886. 



* Vol. ix, p. 77, pi. V, 1886. ^ Op. cit., p. 16. 



