130 NEW YORK STATE MUSEUM 



but on examining its inner aspect, and also that of the secondary (entad) 

 prong, one may determine the exact position occupied by the anterior beak 

 of the mandible when the jaws were closed. Furthermore, the beveling of 

 the inner edge is so regular, and there is such close conformity of all the 

 parts, that it appears practically certain that the teeth were held rigidly in 

 place against the head shield, and incapable of motion either forwardly or 

 laterally. Bashford Dean, however, has expressed the opinion that not only 

 each of the mandibular rami, or "gnathals " as they are termed by him, but 

 the various parts of the upper dentition as well, were capable of a consider- 

 able amount of independent motion. At the same time he acknowledges 

 that these conditions are absolutely unparalleled amongst chordates. In 

 cases like this, the improbable is always to be distrusted. Finally it is to be 

 noted that a portion of the tooth is somewhat deformed — whether as the 

 result of accident during life of the creature, or through pressure during 

 the process of fossilization, it is difficult to say — but whatever the cause, it 

 did not operate so as to crush the more slender prong, or rend it asunder. 

 Formation and locality. " The specimen was found in the Marcellus 

 shale at the foot of Slate Rock fall, near Geneva, Ontario co., N. Y., 25 

 feet below the basal limestone of the Hamilton group, in October, 1890." 

 The original Is now preserved in the New York State Museum at Albany, 



and bears the catalogue number . 



Dinichthys pustulosus Eastman 



Plate 2, figure 6; plate 5. figure 2, 3: plate J2, text figure 25 



1897 Dinichthys pustulosus C. R. Eastman. Mus. Corap. Zool. Bui. 31:38, 



pl- 3. fig- 4 



1898 Dinichthys pustulosus C. R. Eastman. Am. Nat. 32 : 748, text fig. 1,2 



1900 Dinichthys pustulosus C. R. Eastman. Jour. Geol. 8: 32, text fig. i 



1901 Dinichthys pustulosus B. Dean. N. Y. Acad. Sci. Mem. 2; 122 



1902 Dinichthys pustulosus O. H. St John. Am. Nat. 36: 657, text fig. i, a 

 1906 Dinichthys pustulosus L. Hussakof. Am. Mus. Nat. Hist. Mem. 9; 



p. 142, text fig. 22Z' 



A primitive species somewhat smaller than D. t e r r e 1 1 i, generally of 

 about the size of D. intermedius, and distinguished from both by its 



