32 



BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



Comparative Measurements of DinicMhys Species. 



for. At the same time it must be remembeied that the front margin 

 of the plastron in all species of Dinichthys conforms to a peculiar and 

 •well marked type. 



To the right of the left antero-ventro-lateral is a small cleaver-shaped 

 plate (7.5 cm. long by 3 cm. wide), the like of which is unknown among 

 the derm plates of Coccosteids. It certainly does not belong to the 

 dental apparatus, and is excluded fi'om the orbital region on account of 

 its size. There can be no doubt that the plate is entire, or nearly so; 

 but we must confess ignorance as to its position on the body. Just 

 behind the unidentified plate is to be seen a small portion of the verte- 

 bral axis, very imperfectly preserved, together with supports for the 

 dorsal fin. The form of the neural arches is shown with some distinct- 

 ness, as well as their articulation with the proximal row of basal carti- 

 lages. The outer tips of the distal row of basals appear to have been 

 bluntly terminated, or even swollen. 



