MYOMORPHA. 855 



The anterior face of the superior incisor is nearly plane, and it is 

 marked by a weak groove near the inner and a strong groove near the 

 external border In E. elegans this face is convex and without grooves. 

 The molars are rather small for the size of the skull ; their crowns are 

 worn by use. The third is subround in section, and its diameter is about 

 half that of the first; the latter has the anterior odd lobe quite small. 



Measurements. 



M. 



Total length of skull 0380 



Length (axial) to front of orbits 0140 



Length (axial) to palatal notch 0190 



Length (axial) to first molar Ol'^O 



Wiilthat otic bullae 0205 



Width at middle of zygomata 0220 



Width of interorbital space 00(50 



Width between first molars - 0055 



Length of molar series 0070 



Length of first molar 0030 



Width of superior incisor 0015 



This species is dedicated to my friend, W. N. Lockington, the well- 

 known natui'alist of San Francisco. 



ENTOPTYCHUS Cope. 



Paleontological Bulletin No. 30, p. 2, Dec. 3, 1878; Proceeds. Am. Phil. Soc, 1878-'79, p. 64. 



Family 8accomyid<e} The cranium is elongate, and presents inflated 



periotic bones, and slender zygoma. The foramen infraorbitale is small 

 and anterior in position, entering the maxillary bone near its suture with 

 the premaxillary. 



Generic characters. — Molars ---, rootless, and identical in structure. 



4 4 



The crowns are prismatic, and in the young stage present a deep inflection 

 of enamel from one side, the external in the superior teeth, the internal in 

 the inferior. After a little attrition, the connection with the external enamel 

 layer disappears, and there remains a median transverse fossette, entirely 

 inclosed by enamel. The tooth then consists of two dentinal columns in one 

 cylinder of enamel, separated by a transverse enamel-bordered tube. In- 

 cisors not sulcate. 



' Gcomyidce Alston. 



