136 NEW YORK STATE MUSEUM 



being 4.6 cm, and the anterior beak is separated by a considerable interval 

 from the serrated functional margin. The latter terminates posteriorly in a 

 sharp declivity, and this portion of the dental plate is differentiated after 

 the usual manner in Dinichthys. At least eight fine serrations are to be 

 counted along the oral border, quite uniformly spaced. 



The head shield is chiefly remarkable for its relative length as com- 

 pared with the abdominal armor, and for its extreme narrowness anteriorly. 

 The possibility is not excluded, however, that the sinus back of the orbits, 

 although symmetrically developed on both sides in the present condition of 

 the specimen, may be due in part to accidental preservation ; but if normal, 

 a resemblance is to be noted to the configuration of the head shield in 

 Titanichthys brevis, as represented in Claypole's restoration of the 

 latter form.' The suture lines are less undulating than those of Coccosteus, 

 the agreement being rather with Dinichthys in this respect. The rostral 

 plate has become dislocated from attachment with the head shield, but is 

 preserved intact on another portion of the slab (between the right antero- 

 dorsolateral and mandible). Its outline is represented by dotted lines in 

 the figure, as if it were replaced in natural position, but it is impossible to 

 assign definite limits to the pineal and contiguous plates. The median 

 occipital develops a small process in the median line posteriorly, as in some 

 species of Dinichthys. The dorsomedian plate is decidedly Coccosteuslike, 

 and but little emarginate in front, a character which it shares in common 

 with D. h a 1 m o d e u s. The antero-dorsolaterals have strong articular 

 condyles, and much extended anterior margins. The postero-dorsolaterals 

 are slender, triangular plates, not unlike those of Dinichthys. A pair of 

 imperfectly preserved bones, which may possibly be the claviculars, occur to 

 one side of the last mentioned plates ; whatever their true nature, they have 

 at least a form not unlike the clavicular of Titanichthys. The ventrome- 

 dian is narrow and elongate, the postero-ventrolaterals very similar to those 

 of Coccosteus. 



In order to provide data which shall serve for a comparison of parts 



■Am. Geol. 1896. v. 17, pi. 10. 



