THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE IV. VOL. I. 



No. IV.— APRIL, 1894. 



I. — On the Structuee and Affinities of the Genus Solenopora 



TOGETHER WITH DESCRIPTIONS OF NeW SpeCIES. 



By Alex. Broavn, M.B., M.A., B.Sc. ; 



Assistant in the Natural History Department in the University of Aberdeen. 



(PLATE V.) 



TN the present paper I propose to give the results of a series of 

 investigations carried on in the Zoological Laboratory of the 

 University of Aberdeen. Through the kindness of Professor 

 Nicholson, I have had access to his admirable collection of speci- 

 mens of Solenopora, Dyb., and I have also had the privileo-e of 

 using his extensive series of microscopic preparations of the same. 

 With such material, and with additional preparations, I have been 

 enabled to examine, not only species already described, but also a 

 number of new species, of which I shall in this paper give brief 

 descriptions. From examination of all these forms, I find it now 

 practicable to determine the true nature of the genus Solenopora, Dyb. 

 This genus has been described from time to time under various 

 names ; but there is no doubt that Stromatopora compacta of Billino-s, 

 Tetradinm PeacJiii of Nicholson and Etheridge, Solenopora spongioides 

 of Dybowski, and Tetradtum Peachii, var. Canadense of Foord, are 

 in reality names of the same organism. This particular form, 

 described under these various names, is known as occurrino- in the 

 Ordovician rocks of Canada, Esthonia, Scotland, Wales, and Shrop- 

 shire ; and will doubtless ultimately be detected in other reo-ions iu 

 strata of corresponding age. A full description of the species, 

 under the title of Solenopora compacta, Billings sp., was given in 

 1885 by Prof. Nicholson and Mr. R. Etheridge, jun. (Geol. Mag. 

 Dec. IlL Vol. II. p. 529). At a later date Prof. Nicholson further 

 described another species, Solenopora filiformis, from the Craio-head 

 Limestones (Geol. Mag. Dec. III. Vol. V. p. 15, 1888). Still'^more 

 recently specimens were obtained from the Great Oolite of Glou- 

 cestershire and Yorkshire, which, though differing in structural 

 detail, can be readily recognized as another species of the genus 

 Solenopora. Thus, the geological range of this organism can be now 

 extended from the Ordovician series to the Jurassic rocks. Additional 

 specimens have also been examined from Esthonia, and from Craig- 

 head, Girvan ; these showing important structural peculiarities, and 

 reminding one at once of the well-known Nullipores and other 

 calcareous Algae of the present day, 



DECADE IT. YOL. I. NO. IV. JQ 



