The Structure of Dinichthys 



119 



laps the antero'dorso'lateral). The posterior 

 part of the mandible rests on the antero- 

 lateral, a mistake we find in many other 

 reconstructions. 



Besides these photographs, we find in the 

 same book two drawings oi Dinichthys. The 

 first is a redrawing of Newberry's reconstruct 

 tion of 1889, the only difference being that the 

 ''post'maxilla" is omitted and the sub-orbital 

 is made correspondingly larger. The other 

 picture is an attempt to make a total recon- 

 struction of the whole Dinichthys. This 

 drawing is not successful; the position of the 

 antero-dorso-lateral is wrong; there is no 

 contact between the dorsal and ventral cara' 

 pace, etc. 



Two years later Eastman (1897-2) pub- 

 lished his first reconstruction of Dinichthys 

 (D. intermedius Nwb, Text-figure 4). Like 

 Newberry he placed a plate at the back of the 

 sub-orbital and divided the central into two 

 plates. Here, for the first time, the dorsal 

 part of the body carapace (median-dorsal. 



Text-figure 5. 



Hussakof's reconstruction of Dinichthys 



intermedius (1905). 



ADL, antero-dorso-lateral; C, central; DM, dorso-median; 



EO, external-occipital; M, marginal; MO, median-occipital; 



P, pineal; PDL, postero-dorso-Iateral ; PO, pre-orbital; PtO, 



post-orbital; R, rostral. 



antero-dorso-lateral and postero-dorso-lateral) 



is correctly figured, but it is too small in relation to the head shield. The next year East- 

 man (1898.3) made a little change in the reconstruction. He did not divide the central 

 into two plates. The sub-orbital is excluded. Of the body carapace he figured the same 

 five plates, but they are now larger than in the reconstruction of 1897 — nevertheless still 

 too small. Eastman's method of drawing reconstructions became a standard type 

 for later works on Dinichthys. We find it used by Eastman himself. Dean, Hussakof, 

 and others. 



The same year Clark (1898) tried to give some new points of the fine attachments of 

 Dinichthys, but his reconstruction is incorrect for he placed the ''clavicular" upside down. 

 The first true relation between head and body plates is to be found in Hussakof's re- 

 construction of 1905 (Text-figure 5). 



Although the structure of the ventral armor in Dinichthys has been studied by many 

 authors (Newberry, 1875, 1889; Wright, 1894; Dean, 1896 and 1897, Eastman, 1897-2, .3; 

 Hussakof, 1905.1, .2) nobody has been especially interested in the attachment of the dorsal 

 and ventral carapace. The first attempts in this direction were made by Branson in 1908 

 and 1911. His reconstruction of Dinichthys terrelli (Text-figure 6) showed some new and 

 correct alterations. In it the fore part of the ''clavicular" covered the posterior part of 



