PROM NOETH AMERICA, WALES, AND IRELAND. 11 



Both specimens are from the Hamilton Group : fig. 9 from Seneca 

 Lake, ^.Y. ; fig. 10 from Eighteen-mile Creek, Lake Erie Shore, 

 N.Y. 



IV. Gemis Strepula, Jones and Holl. 



Strepula, J. & H. ' Ann. & Mag. Nat. Hist.' ser. 5, vol. xvii. 188G, 

 p. 403. 



1. Strepula sigmoidalts, sp. nov. (PI. II. fig. 4.) 



Size : length '8 mm., height '44 mm. 



A left valve, small, acute-subovate, straight on the back ; posterior 

 edge broadly and obliquely curved to join the ventral margin, which 

 slopes upwards to the sharp antero-dorsal extremity. On the 

 posterior third, and parallel with the hinder margin, is a raised 

 sharp ridge, bifurcating forwards as two feebler ridges, one of which 

 curves back in the antero-dorsal region to form a sigmoid flexure 

 about the middle of the valve and within the larger ridge. There 

 is no published Stre-^mla having these characteristics. 



Erom the Hamilton Group, at Eighteen-mile Creek, Lake Erie 

 Shore, N.Y. 



V. Genus ^chmina, Jones and Holl. 



JScJimincr, J. & H. 'Ann. & Mag. Nat. Hist.' ser. 4, vol. iii. 1869, 

 p. 217. 



1. ^CHMINA SPINOSA (Hall). (PI. III. figs. 4-8.) 



BeyricJiia spinosa. Hall, 'Natural History of New York, Geol. 

 Survey ; Palaeont. New York/ vol. ii. 1852, p. 317, pL a Ixvi. figs. 

 17-21. 



Length. Height. Length of 

 Spine. 



mm. mm. mm. 



f Eig. 4 -8 -46 



I 5 -86 -46 '2Q . 



Size^ 6 -86 -53 ' '66 



I 7 1-2 -8 -73 



^ 8 1-26 -86 -73 



Yalves somewhat Beyrichian in appearance, but the central lobe 

 is replaced by a strong, oblique spine, thick and hollow at the base, 

 either elongate or short, pointing upwards, outwards, and forwards, 

 and sometimes sliglitly bent. Each valve is thickened on its free 

 borders with a raised, rounded, but irregular margin. The area at 

 the base of the spine is hollow and smooth. Sometimes the raised 

 margin is punctate (fig. 8). Eig. 4 is much like Dr. Hall's fig. 21 ; 

 and fig. 5 is like his fig. 20. 



In a thin limestone-seam made up largely of JEchmina spinosa, 

 with Bollia lata (rare), Encrinital joints, Tentaculites, fragments of 

 Trilobites, &c. Erom Lockport, State of New York. Given to me 

 by Prof. 11. P. Whitfield in 1884. 



Also in a dark-grey limestone, composed of Encrinital remains, 

 Tentaculites, small Brachiopods, fragments of Trilobites, and 

 numerous small Ostracods, ^chmma spinosa (very numerous), 



