634 



THK I'AI.KoNToLOCY OK MINNESOTA. 



[Lcpl'l'lllliil filljllllles 



tofore belli 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 XLIIL KK;s. 10-14 



OytherinafabuKtesOoKR/iD, 1843, Proc. Acad. Nat. Sci. Phila., vol. i, p. 332. 



Leperditia fabulites JONES, 1856, Ann. Mag. Nat. Hist., 2d ser., vol. xvii, p. 81); also 1881, iilem, .">th scr. , 



vol. viii, p. 342; also 1891, Contri. Can. Micro-Pal., pt. '.'>. p :*: WHIT- 

 FIELD, 1883, Rep. Geol. Sur. Wis., vol. i, p. 160; ULHKJII, 1MK), Jour. 

 Cin. Soc. Nat. Hist., vol. xiii, p. 173. 



Leperdilia cunudensis, var. josephiana JONES. 1858, Ann. Mag. Nat. Hist., ser. 3, vol. i, p. 341; also 1858, 



Geol. Sur. Can., Dec. 3, p. 94. 



Leperditia fubulites var. josephiana JONES, 1881, Ann. Mag. Nat. Hist., ser. 3, vol. viii, p :(44. 



Leperditio. josephiana JOKES, 1881, Ann. Mag. Nat. Hist., ser. 5, vol. xiv, p. 341. 



SI/.K. 1. Hcluit, Wis., t(E. C.) Length, 12.4 mm.: bight, 7.!> mm.: thickness :,.() mm. 



t 'arapace 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; bight of ends about as 3 is to 4, both obliqely 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 

 otitiisc, scarcely flattened, with a slight furrow on each side near the edge of the 



Consider! ML' tl.:it the ei|iilv;ilent sir:it:i ,,f Kentiieky. Tennessee anil <':in:ul;i. eon lulus no less th;in el<>\ -en -].rri,>< ,,f 

 .1 i kulilr thiil i inly iinc utiiloiibt.'cl speeies of I lie nemis li;is so far IIITTI ill~.-. ivi rnl in t h. Tn'iil.m 



.,f -ti -it, i of tin- in irlhwil ITI, st:iI.->. 

 + In i,'i\ ini lln- -i/i- "f -pi-rlmi'iK. lln-ir rnnilitliin is iniliiMilcil by II" ;iljhn^ ml inns K. O., K V.. unil I, V.. >lKiiiryln^, 



tlM'ly. < nl ire ra I'll pure, rk'til vulve. :iinl Icfl vulve. Wliei'U tlil'se inlli:ils arr not used, i I is lo lie unilersl I lli;il I lie 



