822 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



as to permit some lateral motion. The premaxillary also has no superior 

 condyle articulating with the cranium, but the entire length of its supe- 

 rior margin is applied in a groove of the ethmoid bone, so as to be 

 immovable. Anterior to the premaxillary bones, on the inferior aspect 

 of the ? ethmoid, is situated a pair of large, compressed, doable-edged 

 teeth, whose alveoli are close together. Only one of these teeth is in 

 functional service at a time. In the Erisiohthe penetrans^ the superior 

 surface of the skull is swollen above the fundus of this alveolus, while 

 no such enlargement marks the position of its young companion. 



The compound character of the mandible, and the peculiar mode of 

 articulation of the premaxillary and maxillary bones, entitle this genus 

 to recognition as the type of a family distinct from the Saurodontidce, 

 which may accordingly be called the Erisichtheidce. It is allied to the 

 Saurodontidce in the mode of implantation of its teeth and in the rela- 

 tive extent of the bones of the maxillary arch. 



Three species are represented by the specimens received. They are 

 readily distinguished by the forms of the beaks. In the E. nitida, this 

 weapon is distinguished by the flat superior surface of its distal half. 

 The section in this region is semicircular, a strong angle on each side 

 bounding the superior plane, while at the base the section is a transverse 

 oval. The flat surface is only finely rugose, while the remainder is 

 closely marked with raised ridges, which are generally parallel, but 

 which send off many lateral free or inosculating branchlets. This beak 

 is stout, and contracts abruptly at the tip. It is also recurved, and the 

 form does not appear to be due to distortion. Length from the inferior 

 pair of large basal teeth 0™.155 ; transverse diameter at base 0".025 ; 

 depth at base 0°\021. 



The second species, which [ call Erisichthe penetrans, has a snout of 

 uniformly oval section at all points. The long diameter of the section 

 is transverse. The axis is straight and the form acuminate, the contrac- 

 tion being uniform and gradual to acute apex. Thus it follows that a 

 beak of greater diameter at the base than one of the E. nitida has a 

 more slender shaft. The teeth of the inferior basal pair are, in the spe- 

 cimen described, of large size, and, as in other species, smooth, com- 

 l)ressed, and with opposite fore and aft cutting edges. The surface of 

 the beak is thrown into numerous sharply defined longitudinal ridges, 

 which more or less inosculate with each. There is no difference between 

 the superior and inferior surfaces in this respect. Length of beak from 

 basal teeth 0'".150; transverse diameter at baseO^.OSSj vertical diame- 

 ter at the same point 0"\020; width at middle of the fossae for the pre- 

 maxillary bone 0™.060. 



The third species of Erisichthe is represented by a muzzle of an old 

 individual, which has lost a good deal of its apex by attrition. Its sur- 

 face lacks the sculpture of the other species ; but whether this smooth- 

 ness is due to attrition or not is uncertain. The alveolae for the basilar 

 teeth are empty and almost filled up with bone. The form of the muzzle 



