JULY 



1907] 



SCIENCE 



23 



specimen was transmitted to me by Mr. Fred 

 Boughton Weeks, of the U. S. Geological 

 Survey. 



Three segments are represented in the speci- 

 men, as shown in the drawing. As in Edes- 

 Liis, there are enameled crowns of teeth sup- 

 ported on a shaft of vasodentine. Two of 

 the ci-owns are practically complete, the third 

 lacks a considerable portion. Much of the 

 shaft is splintered off, so that its form and 

 dimensions can not be determined. 



Evidently our fossil does not belong to the 

 genus Edestus, for not only are the bases of 

 the teeth fused so that no traces of the con- 

 stituents appear in the shaft, but the crowns 

 themselves are fused to more than one half 

 their height. The crowns differ from those of 

 all the known species of Edestus in being de- 

 void of all serrations. The crowns of E. 

 giganteus are of nearly the same form and 

 are so closely placed that their edges overlap, 

 but they are not fused. 



Karpinsky in 1899 described a remarkable 

 genus, Helicoprion, related to Edestus, in 

 which a series of about 150 teeth form a spiral 

 of 3J whorls. From the Idaho specimen 

 it is impossible to determine the extent of the 

 whole series or how much it curved during 

 life. However, it certainly was not a species 

 of Helicoprion; for the crowns of the latter 

 are serrated, narrow, elongated, bent forward 

 at a moderate angle, and prolonged so as to 

 reach beneath the second crown forward and 

 nearly to the base of the shaft. In Lissoprion 

 ferrieri the crowns are broader, much shorter, 

 more abruptly turned forward, and prolonged 

 only to the middle of the next crown and far 

 from the base of the shaft. 



Another genus, Campyloprion, was proposed 

 by Dr. C. E. Eastman, in 1902, which had for 

 its type C. annecians Eastman and included 

 Edestus davisii H. Woodward and E. lecontei 

 Dean. The species were believed to have had 

 a bent but not volute shaft and fewer teeth 

 than Helicoprion; while they differed from 

 Edestus in having crowns of different form 

 and bases thoroughly fused. 



In 1903 Dr. Eastman appears to have con- 

 cluded that his species annectans belonged 

 really to Helicoprion and he therefore sub- 



stituted, as type of Campyloprion, Edestus 

 lecontei. This substitution is not permissible, 

 according to the rules of nomenclature. If 

 annectans is really a species of Helicoprion, 

 Campyloprion becomes a synonym of the 

 former; and Edestus lecontei and E. davisii 

 require a new generic name. 



Lissiprion ferrieri differs from Edestus 

 lecontei in various respects. The crowns of 

 the teeth of the latter are narrower, higher, 

 the divisions between the bases are seen to 

 descend to near the base of the shaft and the 

 slope of the axis of the tooth is rather forward 

 than backward. It does not appear probable 

 that the two species belong to the same genus. 



Whether or not there was a longitudinal 

 median channel along the under side of the 

 shaft of Lissoprion, as in Helicoprion, can 

 not be determined from our specimen. 



The anterior end of the specimen is broken 

 at right angles with the axis of the shaft and 

 from it we can learn something of the internal 

 structure. A figure of this would b^ practi- 

 cally identical with that presented by Kar- 

 pinsky of the shaft and crown of his 

 Helicoprion. The central portion of the sec- 

 tion is occupied by a triangular core of spongy 

 vasodentine. Near the base of this triangle 

 are seen the longitudinal canal of the shaft 

 and a smaller canal alongside of it. At the 

 top of the triangle is the canal which leads 

 into the broken crown. The triangle has its 

 base near the lower border of the specimen, 

 and it is probable that this border is very 

 close to the roof of a longitudinal channel. 

 On each side of the mass of spongy vasoden- 

 tine are the denser layers of vascular and 

 tubular dentine and, outside of all, the enamel 

 of the crown. 



The structure above described shows that 

 the bases of the teeth, originally distinct, have 

 become fused so completely that tire bound- 

 aries between them no longer appear even in 

 the microscopic structure. 



The following diagnosis of the genus Lis- 

 soprion may be given : 



Symphysial dentition, a series of fused teeth 

 of unknown number, with broad, high, and 

 laterally compressed crowns, without serra- 

 tion, the crowns fused for the greater part of 



