634 THE PALEONTOLOGY OF MINNESOTA. 
{Leperditia fabulites. 
tofore held as belonging to the genus, are now referred to a new genus on the ground 
that the free edges of their valves are different and the left instead of the right the 
larger. 
Probably seventy-five good species of the genus are known, the greater number 
of which and all the larger forms, are restricted to the Lower and Upper Silurian 
deposits. The earliest forms occur in the Taconic, but it is not till we come to the 
Trenton that the species become numerous.* The Utica slate and Hudson River 
group species are nearly all small and of doubtful affinities. The same is true of the 
Devonian and Carboniferous forms, but in no wise of those which are inclosed in 
Upper Silurian strata, since in this age the genus seems to have attained its greatest 
development both in the way of size and species. 
LEPERDITIA FABULITES Conrad. 
PLATE XLIII, FIGS. 10—14 
Cytherina fabulites CONRAD, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 332. 
Leperditiu fabulites JONES, 1856, Ann. Mag. Nat. Hist., 2d ser., vol. xvii, p. 89; also 1881, idem, 5thser., 
vol. viii, p. 342; also 1891, Contri. Can. Micro-Pal., pt. 3, p 98; Wurr- 
FIELD, 1883, Rep. Geol. Sur. Wis., vol. i, p. 160; ULRICH, 1890, Jour. 
Cin. Soc. Nat. Hist., vol. xiii, p. 1738. 
. Leperditia canadensis, var. josephiana JONES, 1858, Ann. Mag. Nat. Hist., ser. 3, vol. i, p. 341; also 1858, 
Geol. Sur. Can., Dec. 3, p. 94. 
Leperditia fabulites var. josephiana JONES, 1881, Ann. Mag. Nat. Hist., ser. 3, vol. viii, p 344. 
Leperditia, josephiana JONES, 1884, Ann. Mag. Nat. Hist., ser. 5, vol. xiv, p. 341. 
SizE.—1. Beloit, Wis., 7(E.C.) Length, 12.4 mm.; hight, 7.9 mm.; thickness, 5.0 mm. 
2. Minneapolis (L. V.) o 14.0 * se rate cr Si) eet 
3. rs (R. V.) fs 18 bey Ge pv ier as Be age 
4. , (E. C.) ff WS eS ys est yy a0) arets 
5. Dixon, Ill. (E. C.) Oy 122225 us kine er Oo: Die 
6. Lavergne,Tenn.(L. V.) -‘ 1322, a 85 rg ei Qe 
7. Lebanon, Tenn. (EK. C.) se 1OI0 5% “f a3) as AST. oh OSE 
8. = (E. C.) se Yiet5) ae Ge ra linear? Sf edn Oh 
9, Y (HIEDs 8:2, BE Dene: D3 Siete Oo 
10. ib (E. C.) ub 0") 20° ss 421 Ome 4d PEG ame abe 
11. vs (E. C.) ss S:0ies* rs 0e 
Carapace of medium size, obliquely subovate, comparatively long, widest poste- 
riorly; ventral curves moderate, strongest just behind the midlength; cardinal line 
straight, comparing with the length of the valve as 2 is to 3, the two extremities 
almost equally angular; hight of ends about as 3 is to 4, both obligely truncate above, 
the anterior narrowly rounded in the middle; the posterior outline more broadly and 
evenly curved though having the usual backward swing. Ventral edge of carapace 
obtuse, scarcely flattened, with a slight furrow on each side near the edge of the 
*Considering that the equivalent strata of Kentucky, Tennessee and Canada, contains no less than eleven species of 
Leperditia, it is a little remarkable that only one undoubted species of the genus has so far been discovered in the Trenton 
series of strata of the northwestern states, 
+1n giving the size of specimens, their condition is indicated by the abbreviations E. C., R. V., and L. V., signifying, 
respectively, entire carapace, right valve, and left valve. Where these initials are not used. it is to be understood-that the 
dimensions are of an entire carapace. 
