No. 514] DIXICIITHYIJ) ARMOh' PLATES 



or twenty feet of the Marcellus Shale formation. The 

 geological position of the specimen together with its size 

 and the character of its external ornamentation points 

 strongly to its identity with Diniclifhifs ItahiKxInts 

 (Clarke). 2 It is realized perfectly that this identification 

 may prove incorrect but for purposes of convenience the 

 specimen will throughout this paper be considered as 

 belonging to that species. 



The fossil occurs as a probable nucleus for one of the 

 large concretions, though its position in the mass is ex 

 central. It has been laid bare by the removal of a pari 

 of the concretion and apparently has been subjected to 

 weathering for a considerable time. This has resulted 

 in the loss of nearly all of the external ornament, only 

 one or two small patches of bone exhibiting the super- 

 ficial tuberculatum How much of the skeleton has dis- 

 appeared with the missing portion of the concretion it 

 is impossible to say, for diligent search has failed to 

 reveal its presence in the immediate neighborhood. 



The concretions at this horizon are crossed by at least 

 two sets of irregular planes of fracture which have been 

 infiltrated with barite, calcite and other minerals. Y\ e, 

 therefore, have (1) lines crossing the specimen which are 

 incident to the formation of the concretion itself, (2) lines 

 of fracture in the fossil which are independent of struc- 

 tural features and (3) the lines which mark the bound- 

 aries of the different bones. This fact is mentioned here 

 in order to call attention to the many lines in the accom- 

 panying photograph (Fig. 1) which must be di>tin- 

 guished from those which represent organic structures. 



As stated before, the parts preserved are: (1) the 

 nearly complete ventral armor with its elements in nat- 

 ural association and (2) other scattered bones among 

 which a postero-dorsolateral and an antero-dorsolateral 

 stand out conspicuously (see Figs. 1 and 2). 



The Ventral Shield.-ln the median region the antero- 



'Coccosteus (?) halmodeus Clarke. John M. Clarke. New ami MB 

 Species of Fossils from the Horizons of the Livonia Salt Shaft. epo 



