FROM NORTH AMERICA, WALES, AND IRELAND. 27 



11 to 18|, with 12 for the height); cardinal angles distinct, but 

 blunt ; the front end slopes downwards suddenly to meet the antero- 

 veutral curve. With this species, Jones's fig. 6 of pi. vii. 1856, and 

 Meek's fig. 2 a, pi. xvii. 1873, more or less conform, but the former 

 is much rounder, and the. latter is more subovate. 



2. The two smallest of the three whole valves above mentioned 

 remain for L. alta. Fig. 3 b is suboblong, with a straight dorsal 

 and slightly arched ventral border: the posterior extremity is semi- 

 circular, and the anterior has rather less height and curvature ; the 

 antero-dorsal angle and slope are less pronounced than in fig. 2 c ; 

 the hinge-line is also proportionally longer (8 to 12, the height 

 being 7). Fig. 2 a is evidently badly drawn. Jones's fig. 7, pi. vii. 

 1856, is equivalent; and his figs. 8, 9, pl..x. 1858, Meek's fig. 2 «, 

 pi. xvii. 1873, and Whitfield's fig. 8, pi. xxv. (Wisconsin), 1883, 

 are also probable equivalents, though their outlines taper somewhat 

 anteriorly. 



3. The published illustrations resembling the drawing sent from 

 Albany and here reproduced (PI. I. fig. 6) are Prof. Whitfield's 

 fig. e (Lower Helderberg), p. 198, ' Geol. Wisconsin,' vol. i., and a 

 small woodcut in Dana's ' Manual ' and ' Text-book of Geology.' 

 The great depth and elliptic curvature of the postero-ventral, and 

 the narrowness of the antero-ventral region, give a subtriangular 

 outline to the valve. It is probably a variety. 



4. Prof. Hall found L. alta abundant in the Tentaculite-limestone 

 (Waterlime Group) of Albany, Schoharie, Greene, Herkimer, Oneida, 

 and Cayuga Counties in the State of N^ew York (' Pal. N. Y.' iii. 

 p. 374) : and L. Jonesi in the Coralline Limestone (Niagara Lime- 

 stone) of Schoharie and Herkimer Counties (op. cit. p. 372) ; both 

 limestones belong to the Lower-Helderberg group. Meek's speci- 

 mens were from Greenfield, Ohio ; Whitfield's from Waubakee, 

 Wisconsin ; Jones's from Schoharie and from Pennsylvania (all of 

 these being from the Jvower-Helderberg Group), and some from the 

 Upper Silurian of Wellington Channel in the Arctic Regions. 



In the British Museum a specimen (I. 511) of black limestone, 

 with Brachiopods, from the Lower-Helderberg Group, of the Hel- 

 derberg Mountain, New- York State, contains several individuals of 

 two forms of L. alta, Hall ; but the edges of the valves cannot be 

 satisfactorily examined, being, as usual, more or less imbedded in 

 the matrix. 



7. Leperditia nana ?, Jones. (PI. IV. fig. 4.) 



Size: length '73 mm., height -53 mm. 



PI. IV. fig. 4 would be very much like Leperditia (Isochilina) 

 miniitissima, Hall, were its ventral border more elliptically curved 

 and not so semicircular ; nor are the dorsal angles of Hall's species 

 so acute as in our fig. 4, which is probably equivalent to the Lower- 

 Silurian Leperditia (?) nana, Jones, of Canada, Ann. & Mag. Nat. 

 Hist. ser. 3, vol. i. 1858, p. 245, pi. ix. fig. 17. 



From the Bala Beds near Welshpool, Montgomeryshire, North 

 Wales, collected by Mr. J. B. Morgan, F.G.S. 



