THE NAUTILUS. 2S 



cupied by Lamark. Mr. Say intended tliis name to show that his 

 shell was the iMexican analogue of purpureus, 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 cout'uped the situtition.* Examples of U. purpuri- 

 <ttus were collected by Mr. A. A. Hiiikley and distributed as U, 

 strebeli. 



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

 entirely 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 L. S. FRIERSON. 



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

 from beak lo [)Ost-point, which is about half way the height of the 

 shell ; unil)onal ridge low, and the posterior area very narrow ; beaks 

 not high, sculpture not seen ; nacre bluish white ; iri<lescent behind ; 

 teeth double in left, single in right valve; cardinals stout, eiect, lat- 

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

 pallial line obsolete behind. Length, 45 mm. • height, 33 mm.; 

 thickness, 20 mm. 



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

 Miss.). 



Numbers of this species have been in hand for several years and 

 have been distributed largely under the name of •' U. castaneus Lea, 

 Variety." Collectors will rectify their names accordingly. The 

 novelty of the present species was determined by gravid speciniens 

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

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

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

 the beaks in place of being on the teeth. 



In outline it is nearly exactly the same as U. strodeanns B. Id. 

 Wright (Proc. Acad. Nat. Sci. Phil., 1900, Plate 1, tig. 3), but dif- 



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

 "typft'' and misplacing it; and it finally got into the tray of strebeli. This 

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



