THE NAUTILUS. 125 



Long. 2'4, alt. 2-0, diam. T4 mill., (long. 2-3 mill.) ; young, as 

 contained in parent, 0'8 mill. long. 



Habitat: Region of the Great Lakes, in deep water. Lake 

 Michigan : Racine, Wis., dredged (Mr. Geo. T. Marston) ; different 

 places on the Michigan side, partly from a depth of 24 meters ; Pine 

 Lake, Mich., dredged ; Green Lake, Wis., dredged ; from stomachs 

 of White Fish, Lake Michigan, all sent by Mr. Bryant Walker, in 

 1894, and partly since. They \vere believed be a new form, but 

 publication was deferred. 



In March, 1895, Mr. Geo. T. Marston sent me two lots from 

 dredgings, writing: "No. .A. 208, Pis. abyssorum Stimpsou, were 

 from Dr. P. R. Hoy, Racine, Wis. He wrote me that they were 

 first found in the stomachs of White Fish taken in Lake Michigan, 

 near Racine, Wis., in 1870, by a party of gentlemen including Wm. 

 Stimpson and himself. The party were investigating the food of 

 White Fish, then unknown. I quote from Hoy's letter : ' In 1870 

 we drugged in Lake Michigan Wm. Stimpson assisted we got 

 several of the Pisidium and three species of Crustaceans, all of which 

 were new. Stimpson described the several new species the names 

 were published I do not recollect where published but the descrip- 

 tion was written out with the greatest care and were to be published 

 in the Proc. of the Chicago Acad. Sc , of which Stimpson was 

 secretary at the time. All were burnt at the time of the great 

 fire.' ' Mr. Marston subsequently had correspondence with several 

 conchologists, but the matter remained unsettled. The two lots 

 contained different forms of small Pisidia mixed up; but the most 

 numerous and most conspicuous specimens represented the form now 

 described under Stirnpson's name. There is no absolute certainty 

 that this is the same Pisidium the author had described, but it is 

 the nearest in probability, and so to-day by the efforts of Mr. Mars- 

 ton, we can do justice to the deceased scientist. For the above de- 

 scription the writer is wholly responsible. The name (only) Pis. 

 abyssorum has been published by Smith in his "Sketch of the In- 

 vertebrate Fauna of Lake Superior," according to a kind communi- 

 cation of Mr. Bryant Walker. 



The form comes nearest Pis. splendidulum, in size and shape; but 

 it is less inflated, the beaks are less prominent, the color is much 

 paler (whitish), the shell thinner, and the hinge much finer and, as 

 mentioned, partly defective. 



Pis. pauperculum var. Nylanderi n. 



Different from the type in the following points ; it is comparatively 



