1897.] Trituberculy : 1011 
in front of the paracone and protocone, as shown in the dia- 
gram (Fig.6). Thus the inferior entostylid is developed 
near the entoconid, while the superior hypostyle develops near 
the hypocone. The first of the inferior styles to develop is the 
“ metastyle,” a reduplication of the metacone, the well known 
“a-a” of Riitimeyer. 
In all ungulates in which the “ mesostyle” is developed the 
external cusps remain of the same size. In the tapirs no 
“ mesostyle” appears, yet these cusps are symmetrical; but in 
the rhinoceroses, which also lack the mesostyle, the first fact 
to note is the asymmetrical growth of these cusps; the meta- 
cone is elongated while the paracone is reduced and crowded 
up against the parastyle. This point was observed by Cope in 
seeking for a definition of the Rhinocerotide in 1875. The 
rhinocerotine molar, whether of Hyrachyus, Amonodon or Acer- 
atherium, has the further distinction that it is the only type in 
which a complete ectoloph is formed, and second, as Cope has 
already observed, the asymmetry of the external cusps is em- 
phasized by the flattened metacone and conic paracone. Fig- 
ure 2 illustrates also the three projections from the ectoloph, 
protoloph and metaloph, namely, the “ crista,” “antecrochet ” 
and “crochet.” These, with the 
three “fossettes” formed by them, 
were noted and named by Cuvier, 
and, as shown by Falconer, Flower, 
Lydekker and others, are of great 
specific value? We have already 
seen that Cuvier’s term “ fossette” 
may be substituted for the “cement 
lakes” in the horse’s molar. The 
Fig. 18.—Tarır Mortars.. terms formerly adopted, or proposed, 
Primitive ronden: and by Lydekker*,; after English usage, 
=e Tapirus. in and those in German and French 
usage, id already been given in the Table 
7As pointed out by Lydekker, the writer mistakenly transposed these terms 
“crochet: vis and s SRT ” in a former ee, Ban. Mos. bits Zool., 1890, 
81. 
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gie Siwalik Riiiotioüda ts Pal, Inia 
