The Structure of Dinichthys 



117 



It is therefore clear that the reconstruction of a carapace of Dinichthys is a difficult 

 task. Many have tried it, but up to now no satisfactory reconstruction has been made. 



THE OLDER RECONSTRUCTIONS OF DIHICHTHTS 



The first attempt in this direction was made by Newberry. In his paper (1875.1) 

 we find a reconstruction of a Dinichthys "plastron," that is, the ventral shield. In this 

 reconstruction he has placed the sub-orbital in the position of the postero'ventro-lateral, 

 a mistake he himself corrected later in 'Talae- 

 ozoic Fishes of North America" (1889). 



In the latter paper he also gives the first 

 reconstruction of the head shield and part of 

 the dorsal shield (Text'figure 1). The draw 

 ing of the head is nearly correct but the limits 

 between the plates are too schematic. The 

 ''central" is divided into two plates, and the 

 external-occipital (eo) is too large. Besides 

 this, we find a very interesting detail, — a small 

 triangular plate behind the sub-orbital. New- 

 berry called it the post-maxillary but did not 

 describe it in the text. We shall return later to 

 this plate. 



Of the dorsal body carapace we find only 

 the median-dorsal and antero-dorso-lateral in 



the Newberry reconstruction. The median- Text-figure 1. 



dorsal IS too round and placed too far forward, Newberry's reconstruction of Dimchthys 



intermedius Nwb. (1889). 

 d, dorso-median; e, ethmoid; eo, external-occipital; /, 

 frontal; m, marginal; mo, middle-occpital; n, nasal; p, 

 parietal; pm, post-maxillary; pro, pre-orbital; pto, post- 

 orbital; so, sub-orbital; ssc, supra-scapula. 



SO that it comes in contact with the posterior 

 part of the head shield and covers the open- 

 ing between the head and body carapace. 

 The antero-dorso-lateral only touches the 

 median-dorsal. Of the other body plates, 

 Newberry recognized the antero-ventro- 

 lateral, median-ventral, antero-median-ven- 

 tral, antero-lateral (clavicular) and postero- 

 dorso-lateral, but he could not clearly define 

 their position. 



We find in Dean's paper (1891), dealing 

 with the pineal fontanelle of Dinichthys, a 



Text-figure 2. 

 Claypole's reconstruction of Dinichthys 

 interynedius Nwb. (1892). 

 E, ethmoid; EO, external-occipital; F, frontal; M, mar- 

 ginal; ?i, nasal; P, parietal; PrO, pre-orbital; PtO, post- 

 orbital; SO, supra-occipital. 



