4 University of Michigan . 



erals, thin, straight and close together; nacre bkiish-white 

 tinged with sahiion towards the beak cavities and iridescent 

 behind. 



The other specimen (figs. 3-4) is also a female, about four- 

 fifths grown and is accompanied by Raveners original label : 

 "Unio tcncrns — distinct — Lea. Indianfield bridge between 



(illegible) and W'antoot, St. Johns, B. C, So. Car." 



Mr. Mazyck writes: "Wantoot is the name of the old Ravenel 

 I^lantation on the Cooper River." It measures: length 41.5, 

 alt. 26.5, diam. 16 mm. The epidermis is a reddish-yellow and 

 is more distinctly rayed than the type. The nacre and hinge 

 are the same. 



There are evidently considerable individual differences in 

 coloration. All of the Lewis shells are of a greenish-yellow, 

 distinctly rayed with dark green, the rays being more or less 

 interrupted by the lines of growth. But both at Washington 

 and Philadelphia there are shells similar to the Ravenel speci- 

 mens as above described and also those colored like the I<ewis 

 examples. 



Tn order to complete the exposition of the species I have 

 added figures (figs. 5-6) of the largest male shell (No i5754, 

 ■Coll. Walker) in the Lewis set. It agrees with the remainder 

 "of the set in color and in being more distinctly rayed than 

 Ravenel's types. 



As ^Ir. ^lazyck well says (1. c), the discovery of these 

 shells 'seems to solve all doubt concerning the species and set 

 at rest the guess work of students of the American Naiades." 

 There still remains the question as to its position in the sys- 

 tem. 



It seems clear that Ravenel's name can not be retained in 

 any event. It must be held to date from 1892 when for the 

 first time it was correctly figured, though not described, by 



