castai,ie;li,a i 209 



are two vertically striate pseudocardinals in the right valve, 

 the lower the larger and spHt, separated by a parallel-sided 

 socket, and three in the left standing side by side, the middle 

 one the largest, the lower two torn, with a few small tubercles 

 in each valve behind them; one lateral in the right valve and 

 two in the left, s^ranular, and showing traces of vertical stria- 

 tion ; beak cavities deep, not compressed ; nacre purple. 



Animal unknown. 



Type, Costalia sulcata Krauss. 



Castauella sui,cata (Krauss). 



Shell subtrapezoid or suborbicular, inflated, subsolid, inequi- 

 lateral ; beaks full and rather high, sculptured with a few radial 

 bars, of which the anterior are short and faint, while those at 

 the posterior ridge extend well out on the disk ; posterior ridge 

 well developed, subangular, ending in a blunt point above the 

 base of the shell ; hinge line arched, much elevated behind the 

 beaks; dorsal slope obliquely subtruncate; anterior end and 

 base rounded ; surface covered with strong, even, concentric 

 ridges, which become a little blurred in front of the posterior 

 ridge; on the posterior slope there are in addition a few 

 wrinkles ; epidermis reddish-brown, shining ; nacre a little 

 thicker in front. 



Length 50, height 45. diam. 31 mm. 



Surinam. 

 Castalia sulcata Krauss, Zeits. fiir Mai., 1849, p. 99. 

 CastaUeUa sulcata Simpson, Syn., 1900, p. 867. 

 Unio kraussii Lea, Pr. Ac. N. Sci. Phila., VI, 1853, p. 376. 

 Mar gar 011 (Unio) kraussii Lra, Syn., 1870, p. 35. 



A peculiar species, apparently most closely related to Cas- 

 taliua and possibly to be referred to that as a subgenus. The 

 decided regular, concentric sculpture and purplish nacre are 

 characters which I have not seen in any related group. In the 

 shells of Castalina the disks are somewhat flattened; in this 

 species they are convex. 



Lea received this shell from Dr. Dunker under the name of 

 Castalia sulcata Krauss. Believing it to be a Unio, he placed 

 it in that genus, and the name sulcatiis being preoccupied in 

 Unio, he changed it as above. 



