:U 



ZOOLOGICAL AND BOTANICAL ASSOCIATION. 45 



22. Chiton priscus (Munster). Tournay. 



23. „ nervicanus (DeRyckholt). „ 



24. ,, turnacianus (DeRyckholt). „ 



25. „ mempiscus (DeRychholt). „ 



26. „ (Chitonellus) cordifer (De Eon.). Tournay. 



27. „ Thomondiensis (Daily). Co. Limerick. 



28. „ Burrowianus, MS. (Kirkby). Settle, Yorkshire, and pro- 

 bably other species from that locality. 



Upper Devonian, 



29. Chiton laevigatas (F. A. Roemer). Grand. 



30. ,, tumidus (De Ron.). Grand. 



Middle Devonian. 

 Chiton corragatu8 (G. et F. Sandier ger). Villmar. 

 ,, cordiformis (G. Sandb.) 

 „ priscus (G. Sandb. ; non Milmter). 

 „ Sandbergianus (DeRyckh.) 

 „ sagittalis (G. et F. Sandb.). Villmar. 

 ,, n. 8p., Plymouth (Geol. Surv. Collection). 



Upper Silurian. 



33. Chiton Grayanus (DeKon.). Wenlock limestone, Dudley. 



34. „ Wrightianus (DeKon.). „ „ 



Lower Silurian. 



35. Chiton (Helminthochiton) Griffithii (Salter). Cong, Co. Galway. 



By the above list it will be seen, that although the number of fossil 

 species of Chiton is relatively small, when compared with that of the 

 recent, yet they are represented in almost all the series of sedimentary 

 rocks, the Cretaceous formation being the only exception in which they 

 have not as yet been discovered. It is most probable, however, as pre- 

 dicted by Professor De Koninck, that this gap will soon be filled, — it 

 being very improbable that these animals, whose appearance on our globe 

 dates so far back in time as the Lower Silurian, and continuing through 

 all the other formations up to the present day, should have been unre- 

 presented in that geological period. The foregoing list also shows that 

 the Chitonida) were most abundant in the Carboniferous and Permian 

 strata of the Upper Palaeozoic period, and comparatively few in the in- 



