338 Report of the State Geologist. 



Orthis Panderiana. 



Plate 4, figs. 1-3. 



Orthis orthamhonites, Billings. Palaeozoic Fossils, vol. I, p. 77. 

 Orthis Panderiana, Hall. Palaeontology of N. Y., vol. VIII, pt. 1, expl. 

 pi. V, figs. 1-3, and foot-note. 



This shell was identified by Billings with the Orthis calli- 

 gramma^ var. Orthanlbonites, de Yerneuil, under the designation 

 0. orthambonites^ Pander. Pander, however, did not employ 

 this term in a specific, but in a generic sense, though it was sub- 

 sequently taken by von Burn and von Eiohwald as a specific 

 designation to cover all the species referred by Pander to his 

 genus OfjTHAMBorfiTES. As a specific term it must be accredited 

 to von Bug -r, and it is synonymous with some one (it is impossible 

 to say which) of PANDd^B's species. The American shell is quite 

 distinct from the Eussian 0. calligramma var. orthainbonites in 

 its smaller size, fewer and coarser ribs. 



^'Pointe Levis. In the upper part of Limestone No. 2. Quebec 

 groupP (Billings.) 



Orthis? glypta. 



Plate 4, figs. 5, 6. 



Orthis 9 glypta. Hall. Palaeontology of N. Y.,vol. VIII, pt. 2, p. 359, pi. 

 Ixxxiv, figs. 8, 9, 1894. 



Shell small, transverse, with long, straight hinge, making the 

 greatest diameter of the shell ; short along the median axis > 

 marginal outline transversely subelliptical. Pedicle-valve with 

 a broad and low median sinus and generally depressed surface. 

 The exterior bears from twelve to sixteen low, flat plications, 

 separated by narrow sulci, and sometimes with a fine groove on 

 the surface of each. These extend from apex to margins, and 

 are crossed by fine, undulating, subconcentric lines apparently 

 in two oblique sets, producing a peculiarly reticulated or wavy 

 surface, similar to that occurring in the Swedish Silurian species, 

 0. Lovenif Lindstrom. The muscular area of the pedicle-valve is 

 small. Length of an average pedicle- valve, 12 mm., width, 18 

 mm. 



Niagara dolomites. Near Milwaukee, Wiscjnsin. 



