3SS 



THE AMEBIC AX NATURALIST [Vol. LIT 



phalanges closely appressed. The whole attitude of the 

 body strongly suggests some severe spastic distress. The 

 animal may have been a plant feeder and its death and 

 spastic distress due to feeding on some poisonous plant, 

 such as to-day causes tetanic spasms in animals. It may 

 have suffered death from a severe cerebrospinal infection, 

 but whatever the cause of its death, the attitude of the 



animal strongly suggests the effect of disease, and in 

 discussing the history of disease among animals the opis- 

 thotonic position exhibited by fossil skeletons must be 

 considered as indicating a possible diseased condition. 



The correlative phenomenon, pleurothotonos, is less 

 common anion-- the higher vertebrates, but is not uncom- 

 mon among the fishes. This is evidently the attitude as- 

 sumed by the skeleton of the plesiosaur, Plesiotdiint* 

 macrocephahts (Fig. 5), collected by Miss Mary Anning 

 from the Lias of Lyme Eegis, England, and figured by 

 William Buckland in his "Bridgewater Treatise." 4 It is 

 improbable that the head of this long-necked plesiosaur 

 could have been turned into its present attitude by a cur- 

 rent of water, since a force sufficiently strong to have 

 moved the heavy head to one side would doubtless have 



* Vol. H, PI. 19, Fig. 1, 1837. 



