42 



THE GEOLOGIST. 



the Upper Oolitic slates of Cirin, where a lithographic stone some- 

 what resembling that of Solenhofen is quarried, there have been dis- 

 covered remains of emys-like turtles named Achelonia and Hydro- 

 pelta. The Chelone planiceps has been obtained from the Portland 

 beds, and the curiously complicated and to a certain extent " embry- 

 onal " genera Tretosternon and Pleurosternon from the Purbeck. 

 In the cretaceous beds we have discovered true marine turtles 

 (Chelone Camperi, Chelone Benstedii, and Chelone pulchriceps) ; 

 a terrapin (Protemys) has come from the Kentish Rag of Maidstone 

 (Lower Greensand), whilst many species of small turtle (Chelone) 

 are mingled with the phosphatic nodules of the Cambridge Upper 

 Greensand. 



This coracoid bone I recently handed to my friend Mr. Carter 

 Bluke for further and more complete examination, and he has kindly 

 favoured me with the following note : — 



" This specimen consists of the crushed right coracoid bone, 

 viewed from above, of a Chelonian reptile. I have compared it with 

 the homologous bone in the varied kinds of Chelonia, and find a form 

 which resembles it very nearly in the Matamata (Chelys mafamafct, 

 Gray). The family of turtles to which the matamata belongs is to be 

 found in ponds and rivers in warm climates. Dr. Gray tells us that 

 they eat flesh, feed only in the water, and when they swim the whole 

 shell is submerged. As however it is believed that the Trigonia- 

 bearing Stonesfield slate was a sea-deposit, and as there is no doubt 

 whatever that this fossil is really from that bed, there is some degree 

 of antecedent improbability against its representing a freshwater 

 form. Furthermore, taking into account the manifold variations of 

 form which the coracoid bone exhibits in the Chelonia, there is really 

 no reason, morphological or teleological, why a marine species of 

 turtle may not have existed in the Oolitic sea with a coracoid bone 

 so far differing in shape from that of the existing marine turtles 

 (Chelone) as to resemble the homologous bone in the matamata. 

 The turtle of the Oolite co-existed with the JPhascolotherium and the 

 Trigonia, much in the same way as the allied genera of turtles, 

 Chelymys and Chelodina, co-exist on the same continent with the 

 Australian marsupials, whose remains may be perchance washed into 

 the sea where Trigonia still survives. 



" Upon one little fractured bone, however, we must not draw any 

 positive conclusions. No doubt, when the Stonesfield slate shall 

 have been more thoroughly explored, further eA'idences will be 



