1871.] 91 
[Cope. 
one upper incisor. The lobe formula is 12, 14, 1,11 three lobed. The lobe 
of the posterior molar is quite elongate, and divaricates into two angles 
anteriorly, the external of which is almost isolated, almost giving the form- 
ula for the tooth 131. The teeth of both sidesare exactly alike. The near 
approach to isolation of this external angle is due to the deep inflection 
of the posterior inner groove, and very near approach to a corresponding 
incurvature of the lobe. This specimen is referred to the A. sigmodus by 
the analogy to the relation between superior and inferior molars seen in 
A. didelta. In the latter the terminal loop of the inferior m. 1 is more 
simple and the loop of superior m. 8, agrees with it in its simplicity, hav- 
ing nearly the same form. The increased complexity of the anterior loop 
of the inferior m. 1 in A. sigmodus is shared by the m. 3 sup. here de- 
scribed, though not in exactly the same manner. I refer it, therefore, to 
this species with a reservation. 
doeneth Of dental seriesyc hw. dsc usd. ol. lad saeom an. 
Width between middle of m. m. 2 
ee IMCISOLOCUUMILALONb: . seco! swears eee 
ARVICOLA HIATIDENS, Cope. 
Species nova. 
Represented by several molar teeth. These are several times as large 
Va rw, 
as the teeth occupying the same position in any of the species already 
mentioned in this essay, and suggest the genus Fiber. The distinctive 
features of the latter are the compressed oar-like tail, with rooted molars, 
and it is evident that the relationship of this species is not to it. Perhaps 
it is neither an Avicola nor a Fiver, since it differs in the structure of the 
teeth from the known species of both. None of the triangles are isolated, 
but are connected by a narrow strip of dentine, which is narrow posteriorly 
but widens anteriorly until it opens out into the terminal loop. Thus 
the sectional name Anaptogontia may be found ultimately applicable to a 
Separate genus. The separation of the enamel folds merely carries to the 
highest degree that which is seen in the anterior part of the tooth of A. 
sigmodus. 
