274 
PALAEONTOLOGY OF NEW YORK. 
Genus STREPTIS, Davidson. 1881. 
PLATE XIC, PIGS. 33-39. 
1848. Terebratula, Davidson. Bull. Soc. Geol. de France, 2nd sei*., tom. v, p. 331, pi. iii, fig-. 33. 
1859. Rliynchonella, Salter. In Murchison’s Siluria, p. 250. 
1860. Rpirigerina?, Lindstrom. Gotland’s Brachiopoder, p. 364. 
1867. Atrypaf, Davidson. British Silurian Brachiopoda, p. 141, pi. xiii, figs. 14-22. 
1879. Atrypa?, Barrande. Systeme Silurien du Centre de la Boheme, vol. v, pi. 83. P 
1881. Streptis , Davidson. Geological Magazine, vol. viii, p. 150, pi. v, fig. 13. 
1883. Streptis, Davidson. British Silurian Brachiopoda, Suppl., p. 39. 
From what is known of the single species of this genus, S. Grayi, from the 
Wenlock limestone, it would appear that its internal characters are essentially 
similar to those of Triplecia. Mr. Davidson says that he was unable to deter¬ 
mine the precise character of the cardinal process, but an imperfect interior, 
illustrated upon plate xiii, tig. 21, of his Silurian Monograph, shows that it was 
erect, though it appears to have been broken at the point of bifurcation; the 
short spiniform crura are also very distinctly seen, and upon careful examina¬ 
tion of the specimens short dental plates can be seen in the pedicle-valve. 
The exterior of the shell, however, is very peculiar in its bilateral asymmetry, 
the existence of a sinus on each valve, and in the broad free frills at the con¬ 
centric growth-lines.* In respect to its asymmetry the species, as already 
observed, bears very much the same relation to Triplecia as the Mimulus Wald- 
ronensis, from the Niagara fauna in Indiana, does to typical forms of the genus 
Mimulus. The combination of these features with the surface ornamentation, 
and the very small size of the species, will form a valid ground for the recogni¬ 
tion of Streptis as a group subordinate to Triplecia. 
* This feature is more extravagantly developed in the Bohemian species according to the figures given 
by Barrande (Systeme Silurien, vol. v, pi. 83,' figs. 2, 3a, 3d), than in the English forms figured by David¬ 
son. The Bohemian specimens are from Etage _E 2 . 
