8 PROF. T. R. JONES ON SOME PALAEOZOIC OSTRACODA 



Lcperditia (IsochiUna) cylindrica (?) *, Hall, ' Twenty -fourth 

 Eeport State Cab. N. Y.' 1871-72, p. 231, pi. viii. fig. 12; and 

 ' Geol. Surv. of Ohio, Paloeontology,' vol. ii. part 2, 1875, p. lOl, 

 pi. iv. fig. 5. 



The figures given by d'Eiehwald in 1854 (and 1860) differ much 

 one from another t; but the author makes them synonymous. The 

 specimens shown in PI. III. figs. 21, 22, 23, were sent to me by 

 M. d'Eiehwald some years ago, labelled '■'Leperditia viinuta, from 

 Talkof " t, where his figured specimens were also obtained ; and I 

 take fig. 21 to represent the type, putting aside the author's bad 

 drawings referred to above. Figs. 22 and 23 may be varieties or 

 closely allied forms, or, indeed, valves not quite free from the 

 matrix. 



Among the fossil Ostracoda from Cincinnati there are many 

 specimens similar to fig. 21, and with even a more strongly pro- 

 nounced subcentral depression, reaching to the dorsal border. For 

 instance, in No. 59722, British Museum, which is a seam of solid 

 dark-grey limestone (15 mm. thick), shaly on two faces, rusty at the 

 edge, and composed of small organisms, chiefly F. minuta, with 

 Leperditia ? minutissima, and some other, but obscure, Ostracods, as 

 well as Encrinites, Polyzoans, Brachiopods, and Gasteropods, from 

 Covington, Kentucky. Also JSo. 59723 and No. 59725, Brit. Mus. ; 

 in the latter the valves of P. minuta are of a red colour. 



Pigs. 18 and 19 are from the piece of Cincinnati Limestone con- 

 taining ^cJi. Byrnesi and L. hudsonica (?), given me some years 

 ago by Dr..E. W. Claypole, P.G.S. 



If, then, we regard the sulcus as a variable feature, both the 

 conmma and cylindrica above mentioned fall under P. minnta, as 

 defined above. If the sulcus be definitely absent throughout a 

 series, we have AjiarcJiites (Ann. & Mag. Nat. Hist., May 1889, 

 p. 384). It is quite probable, however, that there are in the 

 Cincinnati Limestones more than one or two kinds of little Ostracods 

 having nearly the shape and aspect of the P. minuta here noticed, 

 but furnished with other special characteristics. Among the many 

 associated little valves, exhibiting only their interiors, some evi- 

 dently differ from the above in their outlines ; others, showing 

 exteriors, have an undulating surface, emphasized in many by one 

 or both of their terminal fourths being elevated, and even produced 

 into short spines or tubercles. These, corresponding with the Welsh 



* Hall's Cyther'ma cylhuJrica, 'Pal;i?ont. N.Y.' vol. ii. 1852. p. 14, pi. iv. 

 figs. 8 a, 8 6, fr6m the Medina Sandstone, of Medina, Orleans Co, is really a 

 Leperditia, See ' Ann. & Mag. Nat. Hist.' November 1884, p. 344. 



t Figs. 6 a, h, are subreniform, with the convex edge upwards ; and figs. 2 a, b, 

 ehow a parallelogram with rounded ends. Drawings made from partly im- 

 bedded specimens might give such results. Pri/ziitia fcncra, J. G. O. Linnarsson, 

 ' Kongl. Svenska Vet.-Akad. Handl.' vol. viii. no. 2, 18()9, pi. ii. fig. 70, also has 

 a long oblong shape with rounded ends, and was regarded by Linnarsson as being 

 near P. coiicirum. 



I L. minx fa, Eichw., from Talkof, was referred to as a Primida by Magister 

 Fr. Schmidt, 'Mem. Acad. Imp. Sciences St.-Petersbourg,' sur. 7, vol. x.vi. no. 2, 

 1873, p. 4. 



