1869.] MR. G. BUSK ON FOSSIL REMAINS FROM BORNEO, 41] 
posterior vallum, which extends across from the posterior and external 
angle of the tooth to the side of the posterior column. This val/um 
is In some species deeply emarginate in the middle, and in others 
presents in the middle a dentic/e or small pointed cusp. On the 
inner face are seen the two pyramidal columns separated by the 
entrance of the median valley or sinus; and at the bottom of this 
entrance there is frequently a small tubercle, the median tubercle. 
Within the median sinus is seen projecting into it from the posterior 
column a process of enamel, which is usually termed the “ crochet,” 
and by some the ‘ posterior combing-plate;’’ and in addition to this, 
in many cases, there are one or more small projections of the same 
kind, usually springing from the eufer lamina into the sinus, which 
have been termed the “anterior combing-plate or plates.” They 
might be conveniently designated as the erista or criste. 
To deseribe the Sarawak teeth in the same order :— 
1. On the dorsum the anterior costa (ae, fig. 1) is very prominent 
and prolonged to the base of the crown in its present immature con- 
dition. It is of considerable thickness. The second or median costa 
is very distinct and rounded ; the third or posterior almost obsolete, 
Pir 5 
Dorsum of m. 2, Sarawak tooth. 
being visible only towards the base and quite at the apex. The hinder 
border of the dorsum is much raised, so that between it and the an- 
terior costa the surface of the tooth is deeply hollowed or concave. 
2. The anterior vallum (a. v. fig. 2, p. 412) is strongly developed, 
and the anterior sinus deep, especially at the base. 3. The posterior 
vallum (p.v. fig. 3, p. 412) is deeply emarginate and presents no 
trace of a denticle, and its upper edge is even and not tuberculated. 
4, On the inner face the entrance of the median sinus is contracted 
at the bottom and wide upwards, so that the columns, and especially 
