187] OSTEOLOGY OF LORICATI—GUTBERLET 17' 



Suborbitals. — The suborbital bones, three in number, lie on 

 the lateral surface of the skull. The anterior end of the series is firmly 

 attached to the dorsal edges of the palatine and maxillary, also articu- 

 lated with the prefrontal at its lateral facet. At the posterior end the 

 third bone is attached to the preopercular, thus forming a bridge from 

 the anterior to the posterior ends across the cheek; and also the ventral 

 boundary of the orbit. The suborbitals are plate-like bones. The ante- 

 rior bone is broad, somewhat oval in shape, lying on the surface of the 

 maxillary for some distance from the anterior end. Caudad it is united 

 with the second suborbital bone. The second bone is elongate in shape 

 and about one-half as broad as the anterior one. This bone really forms 

 the ventral boundary of the orbit. The third bone is the longest and 

 passes from the edge of the orbit and is extended caudad, forming the 

 suborbital stay. It is elongate, and is slightly broadened at the posterior 

 end. Near the anterior end of this bone is a small postorbital, forming 

 the posterior edge of the orbit and extending to the edge of the sphenotic. 

 In younger specimens this is merely a cartilage but in more mature 

 forms it becomes ossified. This is a small plate-like bone lying in the 

 dermal tissue. 



Palatine. — The palatine is an irregular bone composed of two 

 portions, a broad plate and an anterior rod. The plate is posterior and 

 is somewhat triangular with the apex pointing caudad. On the lateral 

 surface it is smooth except for some small narrow ridges which extend 

 postero-ventrad from the dorso-anterior end. There is a large facet on 

 the dorsal edge for the articulation with the prefrontal and with an 

 edge of the first suborbital. This facet has a deep pit which extends 

 as a groove on the dorsal edge to the posterior end, and serves for the 

 articulation of the mesapterygoid. The mesial edge of the facet is ex- 

 tended dorsally into a tall process which becomes attached to the ventral 

 edge of the prefrontal. The mesial surface of the palatine is roughened 

 by porous openings and bears a deep groove bounded by the dorso- 

 mesial and the ventro-mesial edges of the bone extending from the 

 anterior end of the posterior portion to the posterior end of the bone. 

 Two kinds of teeth are present on the ventral surface which are like 

 those on the vomer and premaxillary — an inner row of large teeth of 

 the canine variety and outer row of small villiform type, more or less 

 irregularly arranged. The anterior rod-shaped part of the bone is 

 somewhat curved antero-ventro-laterally from the dorsal edge of the 

 triangular portion, directly anterior to the articular facet of the pre- 

 frontal and the suborbital bone. This rod is somewhat flattened dorso- 

 ventrally at the anterior end where it articulates by a ligament with the 

 dorsal surface of the maxillary on the antero-lateral process of the head 

 of that bone. 



