FROM NORTH AMERICA, WALES, "AND IRELAND. 



6. Primitia unicornis (Ulrich). (PI. IV. figs. 8-13.) 



LepercJitia unicornis, Ulrich, ' Journ. Ciiicinn. Soc. Nat. Hist, 

 vol. ii. 1879, p. 10, pi. vii. fig. 4. 



fKg- 

 Size 





Length. 



Height. 





mm. 



mm. 



8 ... 



. . . 1-23 



•8 



9 ... 



. . . 1-3 



•76 



10 ... 



. . . 1-3 



•8 



11 .. . 



. . . 1-4 



•66 



12 ... 



. . . 1-6 



•76 



13 . ,. 



. . . 1-6 



•76 



^ 



Figs. 8-13 would come under AparcJiites, were all Primitian 

 characters absent; but fig. 9 has not quite lost all trace of the 

 Primitian sulcus, and fig. 13 has a shallow residual pit near the 

 middle. Pigs. 8-13 are varieties evidently of one species-enamel}^ 

 Ulrich's '■'Leperditia unicornis.'^ The varying extent of submedial or 

 mid-dorsal depression, the modification of outline and of the posterior 

 tubercle (almost obsolete in fig. 11, which takes on two subcentral 

 tubercles) make the individuals disagree to some extent among them- 

 selves ; and the very numerous specimens in the shale show many 

 modifications of these features. 



Bala Beds, near Welshpool, Montgomeryshire. From Mr. J. B. 

 Morgan's collection. 



Mr. Ulrich's specimens were from the Lower Silurian of Cincin- 

 nati, Ohio. 



7. Primitia minuta (Eichwald). (PI. III. figs. 18 & 19, Cincin- 

 nati ; figs. 21, 22, 23, Eussia.) 



Length. Height, 

 mm. mm. 



f Fig. 18 1-0 ^46 



19 ^8 -43 



Size<; 21 1-53 ^73 



I 22 1-26 ^73 



^ 23 -6 ^3 



Cypridina minuta, Eichwald. ' Bulletin Imp. Soc. Nat. Moscou,' 

 vol. xxvii. part 1, 1854, p. 99, pi. ii. figs. 6 r^, 6; ' Beitriige zur 

 Geologic und Palieontologio Russlands,' 8vo, Moscau (and Moskwa), 

 1854, p. 123, pi. ii. figs. Qa, h. 



Leperditia minuta^ Eichwald, ' Lethaea Rossica,' vol. i. livr. 7, 

 1860, p. 1335, pi. Hi. figs. 2 a, b. 



Cytlieropsis concinna *, Jones, ' Ann. & Mag. Nat. Hist.' Ai)ril 

 1858, p. 249, pi. x. figs. 3, 4 ; Primitia concinna, oj^>. cit. December 

 1865, p. 424. 



* At one titne {op. cif. June 1888, p. 398) I thought that this might be looked 

 upon as Bythocypris figured upside-down ; but I liavo strong doub's on that 

 point, and prefer to keep it among the ahnost furrowless, but not quile even, 

 Primif'ue, there being " a faint dorsal hollow in the original, which may st^ind 

 for the sulcus" {ibid. 1805, p. 424). Such a feature characterizes some Pri- 

 miticB in which the sulcus is becoming obsolete. 



