1903 J Notes on Specimens of Lituites undatus. i6i 



ADDITIONAL NOTES ON SOME CANADIAN SPECI- 

 MENS OF '^ LITUITES undatus:' 



J. F. VVhiteaves. 



Since the publication of a previous paper on this subject, in 

 the October number ot this journal, additional information has 

 been obtained in regard to some of the questions discussed in it. 



In the first place, Dr. W. Y. M. VVoodworth, curator of the 

 Museum of Comparative Zoology at Cambrido^e, Mass., has kindly 

 lent the writer the tjpes of Hyatt's Plectoceras obscurtim, so that 

 it has now become possible to make a direct comparison between 

 them and a large series of presumably authentic specimens of 

 Plectoceras Halli (Foord). Such a comparison has resulted in the 

 conviction that, although P. obscurum may be, and doubtless is, 

 quite distinct from the Inachus uyidatus of Emmons, which Hyatt 

 calls Eurystomiies undatus, there is no appreciable difference, 

 either in external form, in the surface markings, or in the shape 

 and position of the siphuncle, between P. obscurum and P. Haiti. 

 The types of P. obscurum are three in number, one a compara- 

 tively perfect specimen from the Black River limestone at Water- 

 town N.Y., marked 2077; and the others, two fragments from the 

 Birdseye limestone at Watertown, each marked 2078. The speci- 

 men marked 2077 has nearly the whole of one side worn away, 

 but the other side shows the general shape of the shell and its 

 surface markings very well. It is about three inches and a half 

 in its maximum diameter and consists of two entire whorls. The 

 inner whorls, if there were any, are not preserved. Both sides of 

 the specimen show that the whorls are at first so closely coiled 

 that the inner half of the outer whorl is in close contact with ihe 

 one that immediately precedes it, but that its outer half is free and 

 slightly uncoiled. At the anterior end of the shell, the outer 

 whorl is about twelve millimetres apart from that which imme- 

 diately precedes it. And it would seem to be the body chamber, 

 which occupies rather less than one-half of the outer whorl, that 

 is free and separate. The surface markings are precisely 

 similar to those of the fine specimens of P. Halli collected 

 by Mr. Weston at Lorette. On the worn side all the septa 

 but the last are obliterated, and the shape and position 



