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Bashford Dean Memorial Voluyne 



head roof by a solid wall (Text-figure 13 CR). Thus the neurocranium could hardly 

 continue into them. 



A careful study of the head roof of Dinichthys led Stetson (1930) to give another 

 picture of its neurocranium (Text-figure 82A). He conjectured that the neurocranium 

 occupied the central thinner part ot the head roof and was clearly limited by the lateral 



AMV 



Text-figure 83. 



Longitudinal section of the head and body armor in Dinichthys showing the position of the neurocranium 



(hned and cross-hatched) and of the gnathal muscles (lined and numbered). 



Mc, nasal capsule; ?{p. neurocranial process; fm, foramen magnum; /, II, I//, IV, gnathal muscles. 



Outline of spinal column schematic. 



head thickening (LCP). Like Woodward, Stetson thought that the thickened central 

 part of C is a separate plate, but one not limiting the hind part of the brain-case (Text- 

 figure 82 A x-x). The hind part of the neurocranium was narrow and was placed along 

 the median line of MB. Into the deep bilobed impression on the hind part of MB (Text- 

 figure 13 ds) fitted the "cranio-spinal process," which was developed in Dinichthys as in 

 Macropetalichthys . Stetson states that the impressions for the ''musculi depressores 

 capitis" were probably "cavities for branchial apparatus" (Text-figure 82A y-)i). As 

 mentioned before, I cannot accept the relationship between Macropetalichthys and the 

 Arthrodira, and therefore believe that the Arthrodira never possessed the "cranio- 

 spinal process." The bilobed depression on A^ is the attachment place for the musculi 

 levatores capitis. 



When trying to reconstruct the position and size of the neurocranium in Dinichthys, 

 we must first find some definite points, which, for certain, have been in contact with the 



