SYSTEMATIC REVISION 



'Measurements. 



49 



M 



"Length of bases of eight larger molars °-°3 2 



Diameter of large molar: 



Anteroposterior 00 4 



Transverse 00 ° 



Length of three smaller molars 0I2 „ 



Long diameter of a smaller molar 00 4 



The type and only specimen of this species is lost and no specimen can be iden- 

 tified from Cope's description. 



Helodectes paridens Cope. 



Proc. Am. Phil. Soc, vol. xix, 1880, p. 48. 



Type: The same as the genus. 

 Original description: 



"Molar teeth of the two rows subequal in size, and equally numerous . . . . H. paridens. 

 Molar teeth of one row wider, and more numerous than those of the other. . . .H.isaaci. 



"The smallest species of the family is about half the size of the Empedocles 

 molaris. It is represented by a left maxillary and probably premaxillary bone, 

 which are so far covered with the adhesive, hardened ferruginous mud of the forma- 

 tion as not to expose a clean surface. The apices of all the teeth are broken ofF, 

 so that the bases alone remain to indicate their number, form, and positions. 



"Of the molar teeth proper, I count six in the inner and eight in the external 

 row. The two series are close together, and are gently convex inwards. The 

 bases of the teeth are wide ovals, transversely placed. In front of the eighth tooth 

 of the external row (from behind), are two teeth 

 without apparent mates of the internal row (pos- 

 sibly the latter lost). Then follows a tooth of ^/ "- ..jiP " ^.s^^Qf'- 



each row, and in front of these another pair, the W Q \^>Q(?© QT\0£lV* 



external being the larger. Anterior to these, the 



jaw is so split as to remove anv teeth of the inner 



row, if there are any, and one large tooth of the ■* '^^'j&ZZiJZ*"'- * h 



external series stands in the extremity of the 



fragment. This latter exceeds the other teeth in the length and diameter of its 



basal portion. From its position it is probably an incisor. 



"The anterior border of the orbit falls above the third tooth of the external 

 row (counting from behind). The inner border of the maxillary bone is elevated 

 into the ridge convex inwards, as in the other species of this family. The malar 

 base of the zygomatic arch is a moderately stout vertical oval. 



"Measurements. M 



"Length of the dental series. °-°°2 



Length of the molar 6-8 series 02 9 



Width of the two molar series 00 9 >j 



Vertical diameter malar bone OI 3 



Revised description: It is impossible to determine whether the fragment is 

 that of a maxillary bone or a part of the lower jaw. The condition is best shown by 

 the figure. A large part of a skeleton, or of several skeletons doubtfully associated 

 with the jaw fragment, seemingly belongs to some Diadectid animal. 



