936 DR F. R. C. REED ON THE 



Genus Eichwaldia, Billings. 



Eichwaldia personalis, sp. nov. 



(Plate XXIII, fig. 19.) 



Shell rounded, subglobose, strongly biconvex, widest towards anterior end, sub- 

 truncate in front ; margins of valves regular, simple, not sinuated. Pedicle-valve 

 gibbous, swollen, deeper than opposite valve, longer than wide, with long sloping 

 rounded shoulders, somewhat contracted near umbo and reaching nearly two-thirds 

 the length of the valve ; beak high, prominent, inflated, rounded, rising above 

 hinge-line and incurved, nearly touching beak of opposite valve ; apex of beak 

 truncated by large circular foramen with ill-defined small concave false area below 

 it ; interior with pair of long subparallel muscle-scars about half the length 

 of valve. Brachial valve strongly convex, subcircular ; beak swollen, not much 

 elevated, incurved ; interior with median septum extending about three-fourths 

 the length of valve. Surface of both valves smooth ; interior of shell covered 

 thickly with very numerous minute punctse arranged in regular quincunx manner 

 in curved intercrossing closely placed lines (like the engine-turning of a watch-case) 

 about 10-12 punctse to a millimetre. 



Dimensions. — Length of pedicle-valve, 17'0 mm. ; length of brachial valve, 

 14*5 mm. ; width of shell, 15'0 mm. ; depth of shell, 13*0 mm. 



Horizon. — Saugh Hill Group. 



Locality. — Woodland Point. 



Remarks. — Only one specimen of this interesting shell is known to me, and it is 

 in the Sedgwick Museum. The generic reference to Eichwaldia seems probable, 

 and our species much resembles E. gibbosa (Hall),* from the Niagara Formation. 

 The ornamentation is internal and much finer than in E. Capewelli (Davidson),! 

 the only British species hitherto known, and the shape of the shell is different, no 

 median fold and sinus being present. These two Silurian shells are usually placed 

 in the genus Eichwaldia, Billings,} but the original species of this genus, E. sub- 

 trigonalis, Billings, has a smooth exterior, and Schuchert § refers all those with 

 a pitted surface to Dictyonella, Hall. 



* Hall, 20th Rep. New York State Gab. Nat. Hist., 1867, p. 278 ; Hall and Clarke, op. cit., Brach., ii, 

 pi. lxxxiii, figs. 6, 7. 



t Davidson, op. cit., vol. iii, p. 193, pi. xxv, figs. 12-15. 



I Billings, Geol. Surv. Canada, Rep. Progress, 1857-58, pp. 190, 192, fig. 24. 



§ Schuchert, Bull. U.S. Geol. Surv., No. 87, 1897, pp. 210, 220 ; Eastman-Zittel, Text-book of Palaont, vol i 

 (2nd edit. 1913), p. 396. 



