1 8 Bullelin American Museum of Natural History. [Vol. XIX, 



Fig. Q. Protosphymna dimidiata (Cope^. No. 1635. X a 

 Type of Erisichthe dimidiata Cope. Upper jaw, side view. 

 mx., maxilla ; /a/., portion of palatine ; ptnx., premaxilla. 



The premaxilla (Fig. 9, pm%.) possessed four fangs. Its 

 length has been about 75 mm.; the elevation of the hinder 



end about 43 

 mm. The max- 

 illa (Fig. 9, mx.) 

 is 137 mm. long, 

 with a depth of 

 only 17 mm. 

 where narrow- 

 est, then again 

 expanding to near 30 mm. Another bone, probably a jugal, 

 has overlapped the hinder end of the maxilla on the 

 upper side. There is space for about 33 teeth on the maxilla. 

 They are lancet-shaped and are not so strongly inclined for- 

 ward as they are in P . nitida. The same is true of the teeth 

 of' the mandible. Outside of the row of cutting teeth is a 

 row of much smaller teeth. 



The lower jaws are represented by 68 mm. of the anterior 

 end of the left mandible and by nearly the whole length of the 

 right. The tip of the latter and a section of about 30 mm. 

 are wanting, as well as most of the lower border of the bone. 

 In the anterior end of the dentary we find the usual three 

 lancet-shaped fangs. These are succeeded by an interval in 

 which the teeth are very small or wanting. Then follows a 

 single row of cutting teeth, of which those in front and those 

 behind are small. The presplenial is occupied, as in the 

 other species, by two strong fangs. Laterad of these and 

 running nearly the full length of the presplenial is a band of 

 small teeth. This consists of three rows where narrowest. 

 A short distance behind the posterior presplenial fang the 

 band of small teeth is interrupted by what may be a suture 

 between the presplenial and the postsplenial. It is not un- 

 likely, however, that it is only a fracture, since the whole jaw 

 has suffered flexure at this point. In specimens of P. nitida 

 no suture can be seen; although at this point the band of 

 teeth becomes very narrow and thereafter widens' rapidly. 

 Felix was unable to find a suture between the supposed two 

 bones. If they have ever been distinct at any time of the 



