THE NAUTILUS. 



eupied by Latnark. Mr. Say intended this name to show that his 

 shell was the Mexican analogue of purpureiis, and hence his name 

 purpuriatus is a valid name. Mr. C. T. Simpson's remark in his 

 Synopsis that U. strebeli Lea was a young medellinus was an error, 

 and still further confused the situation. 1 Examples of U- purpuri- 

 <ifus were collected by Mr. A. A. Hinkley and distributed as U. 

 strebeli. 



The species occurs in both white and purple nacre, and many are 

 cnlirdy rayless. The example figured is smaller than Say's, but 

 some, of Mr. Hinkley's specimens attained the dimensions given by 

 Say. 



UNIO (OBOVARIA) JACKSONIANTJS, NEW SPECIES. 



BY I.. S. FKIERSON. 



Shell ovate, smooth, rounded before and below, nearly straight 

 from beak to post-point, which is about half way the height of ill-- 

 shell ; umbonal rid ire low, and the posterior area very narrow ; beaks 

 not high. M-ulpture pot seen ; nacre bluish white; iridescent behind ; 

 teeth double in led, single in right valve ; cardinals stout, Mvct, lat- 

 erals not very large : muscle scars confluent behind, separate before ; 

 pallial line obsolete behind. Length, 45 mm. 1 heigi.l. :;;; nun.; 

 thickness. 20 mm. 



Habitat : Pearl River, Miss, (and also in the Yalabusha River, 

 Miss.). 



Numbers of' thi> species have been in hand for several years and 

 have been distribuied largely tinder the name of U. castaneus Le.i, 

 Variety." Collectors will rectify their names accordingly. The 

 novelty of the present species was determined by gravid specin 

 collected by Mr. A. A. Hinkley. and by a comparison with castaneus 

 of the Lea collection by Mr. Bryant Walker. This species has not 

 the female form of castaneus and the dorsal scars are in the bottom of 

 the beaks in place of being on the te-'lh. 



In outline it is nearly exactly the same as U. strodeanus B. II. 

 Wright (Proc. Acad. Nat. Sci. Phil., 1900, Plate 1, fig. ;',), but dif- 



1 This error was caused by someone having marked a young U. medtllinns 

 'type 1 ' and misplacing it; and it finally got into the tray of strebeli. ThU 

 explanation was given by Dr. Wm. H. Dull. 



