On the Geological Distribution of the Rhabdophora. 333 



Fig. 9. Cyrtophium cristatum <$ , magnified. 



Fig. 10. The same : mandible, x 28. 



Fig. 11. The same : left maxilliped, x28. 



Fig. 12. The same : first gnathopod, X'28. 



Fir/. 13. The same : second gnathopod, X 25. 



Fig. 14. The same : single hair from palm of same, xllo. 



Fig. 15. The same : telson and posterior pleopoda, three pairs, X 28. 



XXXVIII. — On the Geological Distribution of the Rhabdo- 

 phora. By Charles Lapworth, F.G.S. &c. 



[Continued from vol. iii. p. 455.] 



Part II. Data. 



Cambrian System. — Although the fact of the existence of 

 Cladophora in the Upper Cambrian rocks has been admitted 

 by palaeontologists since Salter's discovery of Dictyonema 

 sociale in such abundance in strata of this age in Merioneth- 

 shire, it is only within the last few years that the presence of 

 Rhabdophora or true Graptolites in these ancient deposits 

 has been placed absolutely beyond question. Kjerulf, indeed, 

 figured a well-marked Dichograptus [Bryograpius) from the 

 Alum-shales of Christiania in his ' Veiviser,' as early as 1865 ; 

 but its exact horizon is even yet doubtful. Its true Cambrian 

 age, however, is rendered highly probable by Linnarsson's 

 more recent discovery of Dichograptus tenellus &c. in the 

 highest Olenus-beds of Westrogothia*, and an allied form in 

 the Dictyonema-schists of Scania. These strata correspond 

 to the highest portions of the Lingula-flags of Wales, and 

 are unequivocally of true Cambrian age. 



The question of the existence of Rhabdophora in the Upper 

 Cambrian of Britain has also been satisfactorily set at rest by 

 the interesting researches of Dr. C. Callaway. This careful 

 observer detected Graptolites in the Shineton (Upper Cam- 

 brian) shales of Salop as early as 1873 ; and in the following 

 year examples of Bryograptus and Clonograptus from these 

 rocks were forwarded by him to me for identification ; and I 

 recognized at once their striking similarity to the forms figured 

 from the Swedish Cambrian by Kjerulf and Linnarsson. 

 Within the last few months Dr. Callaway has discovered 

 fragments of the first of these genera in the Cambrian rocks 

 of the Malvern Hills. 



* Linnarsson, 'CEfveraigt af Vetenskaps-Ak. Lbrhandlingar,' 1871, 

 p. 794 ; and Geol. Mag., June 187(3. 



