66 



STOLTERFOTH : CRUMMACH LAKE DEPOSIT. 



Fam. RHABDOMESONTID^. Vine. 

 Fourth Brit. Assoc. Rep. on Foss. Polyzoa, 1883, p. 45 of Report. 

 ZoARiuM rod like, branching. Zocecia opening on all sides of the 

 branch, tubular, attached by their proximal extremities to a central 

 rod : orifice of cells obscured by vestibule : wall of vestibule externally 

 ornamented by spines or not. 



Genus RHABDOMESON Young and Young. 

 New Carb. Polyzoa, Young and Young, Ann. Mag. Nat. Hist., Ser. IV., 

 vol. xiii., pp. 335-339, i874- 



10 Ehabdomeson gracile Phill. sp. 



= Millepora gracilis Phill., Palasoz. Foss. 

 This species is rather abundant in the Northern Shales ; and as 

 specimens vary very much, the student is recommended to examine 

 the type very carefully, as in the Yorkshire Shales we have specimens 

 of an apparently alHed species which is closely related to, if not 

 identical with, the American Carboniferous Rhombopora persi??iiHs 

 Ulrich. The Yorkshire specimen will be fully described in the 

 Yorkshire Geo. and Polyt. Soc. Transactions. 



11 Rhahdomeson rhombiferum Phill., sp. 



= Ceriopora id. Phill., Geol. Yorkshire. 

 Ann. Mag. Nat. Hist., Ser. IV., vol. xv., pp. 333-336, Young and Young. 



This is a far more delicate species than the above— especially so as 

 regards the English Shales— though in some of the Scotch Shales the 

 species may be found almost as bulky as some specimens of R. gracile. 



In dealing with these same species in the other shales, it will not 

 be necessary to give so full details as is given now. It is very 

 evident, however, that the micro-palseontology of our rocks is year by 

 year claiming a larger share of attention than has been given to the 

 study in the past. Because of this,, I claim that far more attention 

 should be directed towards the study of the Polyzoa of our rocks — 

 minute though the fragments be — than the species have yet received 

 from mvestigators. ( To be cojitinued.) 



Microscopic Examination of Cnimmach Lake Deposit.— 



Professor G. A. Lebour, in the August number of the Natiiralist, described a pure 

 white marl, like crumbly chalk, as existing at the bottom of this once upland lake. 

 As I have examined the bottom of several Welsh lakes, and have found in them 

 white deposits rich in diatoms, I thought that diatoms ought to be found in the 

 Crummach Lake deposit. Professor G. A. Lebour kindly sent me a small box of 

 the deposit, which I have carefully examined, with the following re*sults : — It con- 

 sists of about 95 per cent, of carbonate of lime, which was dissolved out with 

 hydrochloric acid. The remainder was treated for diatoms, with a result nil. On 

 examining the material under the microscope without chemical treatment, it was 

 found to consist of fragments of freshwater shells, and fine amorphous grains of 

 limestone. I have since heard from Professor Lebour that the lake was surrounded 

 with limestone hills, and these must have supplied the great mass of white powder, 

 which certainly at first looked as if it w^ould be rich in diatoms. I know of no 

 diatomaceous deposit in England, although there are plenty in Scotland, Wales, 

 and Ireland. — Henry Stolterfoth, M.A., M.D., Sci. Sec. of the Chester 

 Society of Natural Science, 60, Watergate, Chester, August 26th, 1884. 



Naturalist, 



