538 Dr. C. I. Forsyth Major on the 
feeble antero-external cusp besides. The milk-tooth is 
similar in shape; only the external cusps and the internal 
cusp are more strongly developed; it is also provided with 
an anterior basal cusp. 
The remains of the external cusps are even yet occasionally 
found in the case of the C.d. of both genera; for Hriculus 
see Leche’s paper *; they are still better developed on the 
C.d. of Echinops, which likewise possesses in addition a 
slight anterior basal cusp. On the C.d. of both genera are 
also found remains of an interior basal cusp. 
Centetes.—As in the case of Echinops and Ericulus, P.1 
sup. differs very little from the milk-tooth and from J/.1; 
it is true that here also the antero-external cusp is somewhat 
more independent and is placed higher up, but the difference 
is perceptible only in teeth which are intact. Apart from 
this, the tooth is more quadrate in outline, and the triangle 
formed by the external cusps and the united para-+ meta- 
cone does not project so far towards the interior as in its 
precursor in the milk-dentition and in the molars.—P. 2 is 
the largest and tallest in the molar series; it possesses a 
fairly large postero-internal cusp, as well as a minute anterior 
basal cusp; of the remaining external cusps only a single 
one, confined to the postero-external angle, 1s present. The 
transition in form between this tooth and the small secodont 
P.3, in which the anterior basal cusp is wanting or only 
sust indicated, is quite abrupt. It is different in the milk- 
dentition: P.d.2 is a tooth of a very elongated shape, with 
external cusps better developed than in the case of its per- 
manent tooth; the foremost of these particularly is more 
strongly developed than in the latter, and especially than in 
the permanent tooth of Hrtculus and Kchinops.—P-d. 3, 
although already strongly compressed longitudinally, and 
without, or only with a slight indication of an anterior basal 
cusp, still shows in fresh specimens traces of the postero- 
external cusps; it exhibits, further, a remnant of an internal 
cusp, and, lastly, an accessory cusp behind and below the 
main cusp (as on P.d.2, P.d.3, P.2, and P.3 of Oryzo- 
ryctes—see below); this, however, is wanting on certain 
specimens, in which case the posterior basal cusp is more 
strongly developed.—Of the milk-incisors the foremost pair 
alone possesses a distinct posterior basal cusp; in the case 
of J.d.2 and J.d. 8, which in the fresh condition are uncinate 
and recurved, this is scarcely indicated. On the other hand, 
* Anat, Anz, xill. p. 52), fig. 4, 
/- 
w ( 2’ Bel, el eee: Gah - << *. 
