110 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.50. 



distance from the front of the symphysis to the rise of the ascending 

 ramus was close to 180 mm; in the jaw of the existing manatee with 

 which it is compared this dimension is 195 mm. The length of the 

 symphysis is relatively the same as in the manatee. Its greatest 

 height is 68 mm.; in the manatee, 83 mm. In the latter animal the 

 upper half of the hinder face of the symphysis forms a concavity; 

 this does not exist in the fossil jaw. The surface which in life was 

 occupied by the horny plate is relatively much shorter than in the 

 manatee, being only 60 mm. long; in the manatee, 80 mm. In the 

 manatee the inner face of the horizontal ramus is flat or even con- 

 cave; this does not seem to have been the case in the fossil jaw. 

 The height of the jaw was evidently less than in the existing manatee, 

 being apparently only 48 mm. at the middle of the length; whereas 

 in the only slightly larger manatee jaw the height is 60 ram. The 

 inferior dental canal is considerably larger than in the manatee, its 

 diameter being 17 mm. Moreover, its outer face is open backwar«l 

 to about the position of the third or fourth tooth. 



Judging from what remains of the sockets of the teeth the latter 

 had a length somewhat greater than in the existing manatee. Three 

 of these sockets occupy a line 45 mm. long; in the manatee used for 

 comparison, 41 mm. The lower teeth appear to have been wider 

 than those of the manatee, but of this one can not be certain. 



Leidy described an upper tooth of a manatee which bears the 

 name Trichechus antiquus, and which was found at Charleston, 

 South Carolina. The fore and aft diameter of the tooth v/as about 

 20 mm.; that of the existing manatee is about 12.5 mm. T. an- 

 tiquus was evidently a much larger animal. Its lov\^er teeth must 

 have had a length of about 24 mm. Evidently the jaw supposed to 

 have been found at Williston belonged to a considerably smaller 

 individual, perhaps to a smaller species, than the one which fur- 

 nished Leidy's type. In the various species belonging to the genus 

 Trichechus there is a continuous succession of teeth which are pro- 

 duced at the rear of the jaw and which move forward. These in- 

 crease in both length and width as the animal grows. Hence the 

 tooth described by Leidy may have belonged to a very large speci- 

 men of the same species as that to which the jaw belonged which is 

 above described. For that reason the jaw is referred provisionally 

 to Trichechus antiquus; but it may, vnih equal probability, have be- 

 longed to an undescribed species. 



ATRACTOSTEUS LAPIDOSUS, new species. 



Plate 26, fig. 4; plate 28, fig. 8. 



In the United States National Museum are a right opercular bone 

 and some scales of a fresh-water gar which are labeled as having 

 been found by L. C. Johnson, in 1885, in the "Mixon bone bed," in 



