70 THE NAUTILUS. 



Spire rather or quite long, acute, 

 the apex slender 2. 



1. Length over 20 mm., apparently- 



related to L. emarginata . . . L. florissantica, n. sp. 

 Length 6 mm. or less, perhaps 



related to L. catascopium . . L. scudderi Ckll. 



2. Small species, about 8 mm. long, 



closely related to L. truncatula . L. sieverti Ckll. 

 Larger species, over 18 mm. long . 3. 



3. Smaller, aperture about half 



length of shell ; apparently re- 

 lated to L. palustris .... X. shumardi Meek & Hayden. 

 Larger, aperture over half length 

 of shell ; apparently related 



to L. stagnalis L. meekii Evans & Shumard. 



L. shumardi and meekii are from the White R. beds ; the others 

 are from Florissant. Lymncea was extraordinarily well developed 

 in the Oligocene of Britain. As my memory serves me it seems 

 that the minor modern groups were already well marked, and it may 

 be considered probable that the types of L. stagnalis, palustris and 

 truncatula, at least, were developed first in the old world, and reached 

 America during the tertiary period. This is also suggested by the 

 fact that the older (Laramie and Eocene) American species of 

 Li/mncea do not suggest the modern circumpolar groups. 



FALSE SHELLS. 



BY C. W. JOHNSON. 



Among the many specimens received from young collectors for 

 determination there are occasionally non-molluscan forms so closely re- 

 sembling shells, that they have been mistaken for mollusks ; in fact, 

 they have even deceived some of the more experienced concholo- 

 gists. 



In the more primitive Crustacea, including the Phyllopoda, espe- 

 cially in the family Estheriidcz and the Gladocera and Ostracoda, the 

 carapace is largely developed and forms a broad oval shell covering 



