34 BULLETIN OI^ THE BUREAU OF FISHERIES. 



The pink heel-splitter, Lampsilis alata (Say) (PI. XXII), is mentioned in this 

 connection only because of the confusion of names. It has about the shape and thick- 

 ness of the white heel-splitter but is always purple or pink and is worthless for button 

 manufacture. The beauty of the nacre and of the teeth makes it useful in novelty 

 work. It occurs in the Mississippi drainage at least as far south as Arkansas, as well 

 as in the drainages of the St. Lawrence River and the Red River of the North. 



The rock-pocketbook, or bastard shell, Arcidens confragosus (Say) (PI. XXI), has 

 little resemblance to the white heel-splitter in form, but its nacre seems to be of the 

 same character. It has the rough exterior of a blue-point, with the inflation of a pocket- 

 book, which accounts for its common names. It is probably related to the S}Tiiphynotas. 

 The species is rare but mdely distributed. 



ELEPHANT'S-EAR GROUP. 



This is the last group of commercial mussels, and the shells possess peculiar features, 

 good and bad. There are only two species to be considered, the elephant's ear, Unio 

 crassidens (Lamarck) (PI. XXIII), and the spike or lady-finger, Unio gibbosus (Barnes) 

 (PI. XXIII). The former is distributed through the ]\Iississippi drainage generally, 

 and occurs also in the Alabama, Tombigbee, and Chattahoochee Rivers. The spike 

 has a very similar distribution, but extends into the St. Lawrence and its tributaries, 

 being common, for example, in the small streams of Michigan. 



As regards economic qualities, the characterization of the two species must be 

 the same, except that the spike has generally a poorer form and is more often inferior 

 in texture. The elephant's ear is broader, more rectangular in form, and heavier. 

 The spike, as the name implies, is more elongate and thinner at the tip. The entire 

 shell is sometimes very thin, as found in small streams. 



Both species generally have an appearance described as "solid," with a thick 

 anterior (butt) portion and often with a very uneven surface. The color may be deep 

 purple, reddish, or salmon, or occasionally white, and is often particularly beautiful. 

 Unfortunately, coloration of any kind detracts from the commercial quality of a shell. 



The thickness is good, but the most favorable feature of the shell is its texture, 

 which is probably equal to that of marine shells. A manufacturer stated that cutting 

 elephant's ears as compared with ordinary hard, white shells was like sa%ving a cake 

 of firm soap as compared ^\4th sawing a board, and quoted a trade maxim: "When 

 you find a pink shell you find a good shell"; that is, a shell which cuts well, although 

 its color may make it undesirable. Analysis shows that the color is a feature of the 

 organic matter in the shell and not of the crystalline or lime content. No clue has yet 

 been obtained as to the nature of the coloring matter, nor has any entirely satisfactory 

 method of bleaching been discovered, unless quite recently. If the color could be 

 removed from the nacre by a cheap process that would not injure the texture or luster 

 of the shell, the elephant's ear would become a most popular material. 



Elephant's ears, when purchased in mixed lots, can be used to advantage for the 

 production of smoked-pearl buttons, if stained with silver nitrate. Occasionally car- 

 load lots of this shell have been purchased on the rivers toward the close of the season, 

 but the practice has been discouraged by the tendency of shellers to throw in all 

 manner of pink, purple, and otherwise useless material. Both species are used in 

 making novelties. These mussels are probably short-term summer breeders. 



