REPORT OF THE DIRECTOR IQII 



137 





W^ KiA/ 



a 



Dentition. It is well established that Scaumenacia had typical 

 dipnoan dental plates. Whiteaves [9] figured a portion of such a 

 plate showing a group of pointed denticles arranged in rows ; and 

 Jaekel [4] has given a figure of a complete lower dental plate. 



Figure 5-b represents an upper, or palato-pterygoid, dental plate 

 drawn from a small specimen in the American Museum collection 

 (7662). This plate and the one figured by Jaekel show plainly that 

 Scaumenacia had a Dipterus-like dentition. The dental plate shows 

 seven rows of small pointed and slightly compressed denticles. The 

 row^s do not radiate from a common point but from a smooth area 

 near the inner angle of the tooth. The number of denticles in a 

 row varies from two or three in the innermost, to seven or eight in 

 the outermost row. 



Besides a dipterine plate I have found 

 vomerine teeth in Scaumenacia (figure 5-a). 

 These are of great importance considering 

 the rarity of specimens of these teeth in the 

 extinct dipnoans. They were found in 

 their natural position in a large fish in the 

 American Museum (no. 7656). When col- 

 lecting the specimen in the field it was 

 accidentally struck so that the snout broke 

 off as a small fragment. On the inner sur- 

 face of this, and right in advance of the 

 most anterior denticles of the upper and 

 lower dental plates, could be seen, above, 

 a pair of small, thin vomerine plates (fig- 

 ure 5-a). They are broader than deep, 

 with the lower edge cut into four unequal, 

 sharp teeth or serrations. In view of this serrated con- 

 dition the vomerines of Scaumenacia may be regarded as more 

 primitive than those of the adult Neoceratodus. They resemble 

 somewhat the vomerines of the embryonic Neoceratodus as described 

 by Semon [5]. The small fragment of matrix containing these 

 teeth was unfortunately lost; not, however, before a careful figure 

 of the vomerines had been prepared. 



Scales and lateral line. Regarding the scales, Whiteaves wrote 

 [9, p. 108] : '' Scales thin, cycloid, imbricating with exposed sur- 

 faces concentrically striated and marked also with exceedingly min- 

 ute radiating lines, which latter are only visible under a somewhat 

 powerful lens." The superficial ornament of the scales is indeed 



Fig. 5 Scaumenacia curta 

 (Whiteaves) ; dental plates and 

 scale, a, vomerine teeth; b, pal- 

 ato-pterygoid dental plate; c, 

 portion of a scale, showing or- 

 namentation (enlarged) 



