OSTEACODA. 689 



Bythocypris? curta.] 



ByTHOOYPRIS (?) CURTA, «. Sp. 

 PLATE XLIV, FIGS. 36-38. 



Size. — Length 1 .03 mm.; hight 0.75 mm.; thickness 0.48 mm. A larger specimen has a length of 

 about 1.5 mm. 



This is an unusually short, subovate form, the ends being nearly equal and, with 

 the dorsal margin, forming an almost regular elliptic curve; ventral outline straight 

 centrally; surface smooth; valves moderately and uniformly convex, one larger and 

 strongly overlapping the other above) below and at one end. The end having no 

 overlap is slightly narrower than the other. 



The subequality of the ends, especially as regards thickness, makes it difficult 

 if not impossible to determine with certainty which is the right and which the 

 left valve. As a Bythocypris the larger of the two must be on the left side, and if this is 

 correct for the species, then the.blunterof the two ends would be the anterior. In 

 Macrocypris, a genus containing mostly elongate species, the right valve overlaps, but 

 the carapace in the present species is too short for that genus. Of known species B. 

 ovata Jones and Holl, a Wenlock form originally described as a variety of Cytherellina 

 siliqua,* may be nearest, but differs like all other species of Bythocypris in being 

 longer. . 



Formation and locality.— Middle third (Bhinidictya bed) of the Trenton shales, St. Paul, Minnesota. 



Bythocypris granti, n. sp. 



PLATE XLIV, FIGS. 39-42. 



Size.— Length 1-.40 mm.; hight 0.68 mm.; thickness 0.7 mm. 

 Length 1.17 mm.; hight 0.57 mm.; thickness 0.6 mm. 



Valves strongly convex, especially so ventrally, somewhat elongate elliptical in 

 outline, the ventral margin convex but not so much as the dorsal, the ends sub- 

 equally rounded but with the posterior one a little blunter than the anterior; surface 

 smooth. 



This species is readily distinguished from B. cylindrica Hall, by its more equal 

 ends and convex basal outline. It seems to be closely related to B. concinna Jones, 

 of the Wenlock shales of England, but the outline is a libtle different and the valves 

 thicker in the ventral part. The left valves of Krausella incequalis and K. arcuata 

 are somewhat similar yet not enough so to render confusion between them at all 



likely. 



The species is named for the promising geologist, Dr. Ulysses S. Grant, of the 

 Geological Survey of Minnesota. 



Formation and locality.— Kiddle third (Rhinidictya bed) of the Trenton shales, St. Paul and Minne- 

 apolis, Minnesota. 



*Ann. Mag. Nat. Hist., set. 4, vol. ili, pi, xiv , flg. i; 1869. 

 -44 



