this product was remarkable for its persist- 

 ency. 



The product of experiment number 2 is, in 

 part, a silicate of zinc which somewhat re- 

 sembles willemite in the color of its fluores- 

 cence, but it differs from willemite in being 

 intensely phosphorescent. It is worthy of 

 notice that without the trace of manganese 

 the resulting zinc silicate will show no fluo- 

 rescence nor phosphorescence, in this respect 

 resembling the non-fluorescent specimens of 

 willemite. An inference may be drawn from 

 this fact as to one of the probable causes of 

 the brilliant green fluorescence of the wille- 

 mite found in Franklin, N. J. 



W. S. Andrews. 



Schenectady, N. Y., 

 December 29, 1903. 



PALEONTOLOGIGAL NOTES. 

 PLEUEOCCELUS VERSUS ASTRODON. 



In the Annals of the Carnegie Museum, 

 Vol. II., p. 12, Mr. Hatcher reaches the con- 

 clusion that the dinosaurian genera Pleuro- 

 coelus and Astrodon are identical, and that 

 Astrodon, having priority, should stand; 

 furthermore, Mr. Hatcher concludes that 

 Pleurocodus may be the young of some larger 

 species. Both of these conclusions are, it 

 seems to me, open to doubt. The vertebrse 

 and foot bones ascribed to Pleurocmlus greatly 

 outnumber all the other vertebrate remains 

 obtained from the vicinity of Muirkirk, Md., 

 the locality where most of the vertebrates of 

 the Potomac formation have been collected. 

 The small, slender, cylindrical, blunt-pointed 

 teeth supposed to be those of Pleurocmlus also 

 outnumber all other teeth found in the Po- 

 tomac formation, so that there is good reason 



*From Franklin, N. J. 



to believe the identification to be correct. 

 The type of Astrodon was an imperfect, large 

 tooth, thrice the size of any ascribed to 

 PleurocceluSj and not over four of these teeth 

 have been discovered, while there are none of 

 intermediate size between the two. A section 

 of a tooth of Pleurocoelus shows that the 

 enamel is proportionately much thicker than 

 in the tooth of Astrodon figured by Leidy, 

 and while this may be partly due to a difier- 

 ence in the planes of the respective sections 

 this evidence is proffered for what it is worth. 

 Finally, it may be said that no large vertebrae 

 or foot bones similar to those of Pleurocoelus 

 have as yet come to light, so that for the 

 present it would seem well to accept the 

 validity of this genus. 



THE ARMOR OF ZEUGLODON. 



There is such a determined effort nowadays 

 to derive the whales from armored ancestors 

 and to foist a shield and buckler upon Zeu- 

 glodon that it requires some courage to sug- 

 gest that at present there is no good evidence 

 that either of these theories is correct. If 

 any living cetaceans carry with them traces 

 of armor, it seems strange that no partly 

 armored form has come to light among the 

 abundant cetacean remains found in Miocene 

 deposits. As for Zeuglodon (Basilosaurus), 

 the only armor that undeniably belongs to 

 this animal consists of a few, somewhat pyri- 

 form, slightly keeled ossicles, the largest some- 

 what greater than a man's fist. There are two 

 of these in the collection of the U. S. National 

 Museum and no other traces of armor have 

 been found, either by Dr. Andrews in Egypt, 

 or by Mr. Schuchert in the southern states. 

 There is no reason to suppose that the ir- 

 regular fragment in the Koch collection, fig- 



