Teeth in the Centetide. 535 
Since the united para- and metacone extends to the inner 
margin of the tooth, and the ‘ protocone,” from Potamogale 
onwards, appears more and more coalesced with the former, it 
is probable that the continually diminishing ‘ protocone”’ has 
gradually been absorbed by the para-+metacone. The state 
of the case in the molars of Hriculus and Echinops is similar 
to that which is seen in Centetes ; there is no occasion here 
to go further into details—In Oryzoryctes the protocone is 
still of relatively considerable size, bicuspid in the case of the 
two anterior molars and in P.1, most distinctly so in the 
latter; the posterior cusp, which appears unusually little 
developed in M.1 and MM. 2, will have to be interpreted in the 
same manner as in Solenodon.—In Microgale Dobsoni also 
the feebly developed talon is bicuspid.—In Limnogale it 1s 
even tricuspid in the case of perfect teeth_— The maximum of 
reduction seen in Centetides occurs in Hemicentetes. The 
talon is still indicated only in the case of M.1; the external 
cusps, with the exception of two, on the anterior and posterior 
margin, are to all intents and purposes suppressed ; the united 
para- and metacone is of considerable height. Moreover the 
teeth are compressed longitudinally, parallel to the longitu- 
dinal axis of the body, the last two upper molars less so than 
the rest.— Geogale is not known to me by personal examina- 
tion. 
After the above analysis of the molar components in the 
Centetide it is not difficult to give an answer to the question 
with which we started—namely, whether the form of molar 
that occurs in this family (as also in the Solenodontide and 
Chrysochloride) is to be regarded as primitive, as is pretty 
generally assumed, or, rather, as the result of a reduction. 
It is manifest that it is only the richly developed external 
cusps which are a primitive feature, because, indeed, throughout 
the mammalian class these cusps present themselves as an 
archaic phenomenon. I do not venture to go so tar as Winge, 
who regards them as homologous with the three cusps of 
the Triconodon-tooth. But we found them developed to the 
fullest extent in Laramie teeth, next to which they are most 
pronounced in the low groups Polyprotodontia and Insec- 
tivora ; in other orders in the case of their oldest represen- 
tatives. 
Undoubtedly of a secondary character, and to be regarded 
as a retrogression, is, according to what has already been 
stated, the fusion of the “ paracone” and “ metacone ’’—a 
phenomenon met with elsewhere among mammals only in 
premolars and rarely in the .3*, The united para- and 
* It is only in Notoryctes, which in other respects also is highly 
