170 Bashford Dean Memorial Volume 



A; from inside — B). This drawing is based on material in the Buffalo Museum. 

 All the plates belong to one specimen so one cannot doubt that their relation, position 

 and si2;e are correct. MD is not shown on the figure; only its overlapping margins on 

 ADL and PDL are seen. The upper part ot the last two plates was in reality curved 

 backwards. To make it clearer it has been flattened in the drawing. The previously 



Text-figure 55. 

 The relative positions of the side plates in the body carapace of Dinichthys: A, from 



outside : B, from inside. 



Figure based on material from the Buffalo Museum 



mentioned triple sensory canal on ADL and PDL is shown by dotted lines in Figure A. 

 The complete outline of the plate PL is not visible either from the outside or from the in' 

 side. Therefore its contour is dotted in figure B. ■ 



These two drawings show how strongly the single plates of the dorsal shield were 

 connected. They formed a verysolid and massive girdle, which served not only as a 

 protecting armor, but also as the place where the strong body muscles were attached. 



THE VENTRAL SHIELD 



The ventral shield or "plastron" was well known in former times. As early as 1875 

 Newberry gave a fairly good figure of it, and in 1894 Wright published an absolutely 

 correct reconstruction. Later Eastman, Dean, Hussakof, and Smith described and figured 

 it several times. 



But the connection between the dorsal and ventral shields has never been studied and 



