Yol. 56.] AND OLDHAM IA. 285 



(10) Salter, J. W. Catalogue of Cambrian & Silurian Fossils in the Wood" 



wardian Museum, Cambridge, pp. 1 & 2. 1873. 



(11) Bailt, W. H. ' Figures of Characteristic British Fossils ' vol. i, p. x, fig. 1, 



& pi. i. London, 1875. 



(12) Kjerulf, Th. ' Die Geologie des Sudlichen u. Mittleren Norwegen ' (German 



edit, by A. Gurlt), pp. 66, 133, 195 & 196. Bonn, 1880. 



(13) Kcemer, Feed. 'Lethaea Geognostica' pt. i, vol. i, p. 136 (with figure). 1880 



& 1897. 



(14) Nathorst, A. G. ' Om Spar af nagra Evertebrerade Djur och deras Paleonto- 



logiska Betydelse ' Kongl. Svensk. Vet.-Akad. Handl. vol. xviii, No. 7, pp. 1- 

 104 & pis. i-xi. 1881. 



(15) Malaise, C. 'Sur la Decouverte de VOldhamia radiata, Forbes, dans les 



Terrains Anciens du Brabant ' Bull. Acad. Roy. Belg. ser. 3, vol. v, p. 4. 

 1883. 



(16) . 'Sur un Nouveau Gisement de VOldhamia radiata, Forbes, dans le 



Brabant ' ibid. p. 749. 



(17) Etheridge, R. E. ' Manual of Geology ' by John Phillips, pt. ii, p. 32 & 



pi. i. London, 1885. 



(18) Jolt, J. ' On the Permanency of Frost-marks & a Possible Connexion 



[thereof] with Oldhamia radiata & O. antiqua ' Sci. Proc. Roy. Dubl. Soc. 

 n. s. vol. v, p. 156. 1886. 



(19) Sollas, W. J. ' On a Specimen of Slate from Bray Head, traversed by the 



Structure known as Oldhamia radiata ' ibid. p. 355. 1886. 



(20) -. ' Supplementary Remarks on Oldhamia ' ibid. p. 358 & pi. viii. 1886. 



(21) Jolt, J. ' On a Peculiarity in the Nature of the Impressions of Oldhamia 



antiqua & O. radiata ' ibid. p. 445. 1886. 



(22) Bonnet, T. G. 'Nature' vol. xxxv (April 21st, 1887) p. 581. 



(23) Barrois, Charles. ' Note sur l'Existence du Genre Oldhamia dans les 



Pyrenees ' Ann. Soc. Geol. Nord, vol. xv, p. 154. 1888. 



(24) Sollas, W. J. ' The Geology of Dublin & its Neighbourhood ' Proc. Geol. 



Assoc, vol. xiii, p. 94. 1893. 



(25) . ' On Pucks ia MacHenryi, a New Fossil from the Cambrian Rocks of 



Howth ' Sci. Proc. Roy. Dubl. Soc. n. s. vol. viii, p. 297. 1895. 



EXPLANATION OF PLATES XVII-XIX. 



Plate XVII. 

 [For toe photographs on this Plate I am indebted to Mr. J. A. Robinson.] 



Fig. 1. Ichnium Wattsii, gen. et sp. nov. From a photograph of a specimen 

 in the Oxford University Museum. X 09. 



2. Oldhamia radiata, Forbes. From a photograph of a specimen in the 



Oxford University Museum. X 2. 



The club-shaped terminations of the radial grooves are well dis- 

 played in places, particularly about an imaginary line joining the 

 centres of the two individuals on the slab. A joint crosses the slab 

 obliquely, cutting through the lower of the two individuals ; on the 

 lower left-hand side of the joint a layer of the rock has been flaked 

 off, so that the exposed surface here lies 4 mm. below the general 

 level, at.d the rays seen upon it are the outward continuation of the 

 structure, which to the right and above lies concealed 4 mm. below 

 the markings actually represented. The rays of the lower surface are 

 also the downward continuation of the marking which once lay 4 mm. 

 immediately above them : notwithstanding this, they are seen to 

 continue the direction of the rays on the preserved upper surface, and 

 are scarcely inferior to them in sharpness of impression. (Oblique 

 fractures sometimes reveal the extension downward of one system of 

 grooves through a thickness of 1 cm.) 



3. Ola.hamia antiqua, Forbes. From a photograph of a specimen in the 



possession of Prof. J. Joly, D.Sc, F.R.S. X 2. 



4. Tracks of a living worm. (After Nathorst.) 



Q. J. G. S. No. 222. x 



