THE NAUTILUS. 51 



U. deciivis. In consequence there are produced in this way many 

 variations and malformed specimens. 



A colony of rough, bla.ck and corroded U. tetralasmus was taken 

 from a stream across which a boy could jump, and planted in a rail- 

 road tank of fifteen acres, newly made by the K. C. S. R. R. Two 

 years after, one of their progeny was taken from this tank, with a 

 yellow, smooth epidermis as hard and glossy as glass, and as distinct 

 from U. deciivis as lateolus is from ligamentinus (see pi. iii, upper 

 figure). 



In this connection, the writer would remark that in an article 

 published several years ago (NAUTILUS XI, 3), under the caption 

 " Conchological Notes from Louisiana," he spoke of the above- 

 mentioned difference in habitat of U. deciivis and U. tetralasmus. 

 But at that time all of his specimens were named according to preva- 

 lent tradition, and he exactly reversed their names. 



Like many other young collectors, the writer has in this way sent 

 out numbers of shells with erroneous names, and helped to make 

 confusion worse confounded. He hopes herein to correct at least one 

 of these errors, and at the same time to render justice to that most 

 excellent naturalist, Thomas Say. 



By comparing the figure with that given by Conrad in his Mono- 

 graphy, page 45 (and on which Mr. Call's synonymy is based, no 

 doubt,) it will be seen that the shells of U. declicis and U. tetralas- 

 mus are utterly unlike. 



EXPLANATION OF PLATE III. 



Upper figure. U. tetralasmus Say. R. R. tank, De Soto, La. 



Middle figure. U. deciivis geometricus Lea. Dried bed of Lake 

 Connisnia, La., showing stunting and periodicity of growth induced 

 by successive droughts. 



Lower figure. U. deciivis Say. Bayou Plaquemine, La., at 

 Church Point. 



A NEW SPECIES OF METZGERIA. 



BY WILLIAM HEALEY DALL. 



The genus Metzgeria Norman, has hitherto been known from a 

 single species, the pusilla of Sars or alba of Jeffreys. This is re- 

 ported from the coast of Norway and the northeastern North At- 



