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THE AMEBIC AX X ATE BALIS I [Vol. XLIII 



are believed to have been broken or to have weathered 

 away. If this is the case we have exposed the actual lat- 

 eral outlines of the two median plates. The shape of the 

 entire ventral shield is quite accurately indicated by the 

 outer margins of its constituent plates in spite of fractur- 

 ing and some displacement. The left antero-ventrolateral 

 still retains a small patch of the exterior surface showing 

 a tuberculation similar to that of a Dinicthyid cranium 

 from Manlius, N. Y., which has been referred by Eastman 

 to D. halmo&eus? A few obscure tubercles are also 

 present on the left postero-ventrolateral. As exhibited 

 in this specimen the two median plates appear to be quite 

 flat. The antero-ventrolaterals are much crushed, but 

 apparently were slightly convex on their ventral surfaces. 

 The postero-ventrolaterals show convexity on their outer 

 or ventral surfaces. 



Bones without the Ventral Shield.— The most con- 

 spicuous of these are the postero-dorsolateral and the 

 antero-dorsolateral. The former of these is flat, and 

 though it is much weathered, it appears to furnish us 

 with about the outline of the original plate. The latter 

 is decidedly convex and though much weathered it shows 

 the articular projection and the canal. 



Above (forward of) the ventral shield is a confused 

 mass of bones, some of them exhibiting sharp tooth-like 

 denticles, while beyond this again is another poorly pre- 

 served antero-dorsolateral exhibiting both the canal and 

 the articular projection. No cranial plates can be made 

 out with certainty, though the bone marked 1 in Fig. 2 

 might be interpreted as a suborbital, while at 2 is a bone 

 suggesting an antero-supero-gnathal. 



Comparison with other Specimens 

 As far as the author knows, only two other specimens 

 of Dinichthys with the ventral armor plates in natural 

 association have been recorded. The first specimen was 



3 N. Y. State Museum Memoir, 10, p. 128, pi. 10. 



