BRACHIOPODA. 257 



Phillips,* which form Mr. Davidson has regardedf as but a variety of Phillips' 

 Spirifer crenistria. 



This well known and widely distributed species (according to current au- 

 thority), Spirifer crenistria, Phillips {= Streptorhynchus crenistria), may hence Ije 

 taken as the type of Orthothetes ; and since this fossil, as recognized, is sub- 

 ject to considerable variation in the regularity and elevation of the umbo of the 

 pedicle-valve, which is usually normal and symmetrical, but sometimes much 

 distorted, it opens the genus to the reception of species in which this irregular- 

 ity is usually present, and to those in which this condition does not appear. 



Genus HIPPARIONYX, Vanuxem. 1842. 



I'LATE IX, FIGS. Si-m ; and PLATE XVa, FIGS. 'J-U. 



183S. Leptcena unguifornm, Conrad. Fir.st Ann. Rept. Palseont. Dfpt. N. Y. State Genl. Survey, 



\i. 112 (not described). 



1840. Strupliomena uii.guiformi.% Conrad. Third Ann. Rept. Paheont. Dept. N. Y. State Geol. Survey, 



p. 203 (not described). 



1841. Atrypa unguiforiiiis, Conrad. Fifth Ann. Rept. Palseont. Dept. N. Y. State Geol. Survey, 



p. 36 (not described). 



1842. Hipparionyx pmxiiiius, Vanu.ke.m. Geology of N. Y. ; Rept. Third Dist., p. 124, tig-. 29, No. 4 



(not H. amsimUis noi' H. similar'ts, Vanuxem, \>. 124). 



1843. Atrypa u.ngiufonnls, (Conrad) Hall. Geology of N.Y.; Rept. Fourth Dist., p. 149, fig. 60, No. 4. 

 18.i9. Oithis hlpparioiiyx, Hall. Palieontology of N. Y., vol. ill, p. 407, pi. Ixxxix, tigs. 1-4 ; pi. xc, 



tigs. 1-7 ; pi. xci, tigs. 4, 5 ; pi. xciv, fig. 4. 

 1860. Orthis unguiforiais, Emmons. Manual of Geology, p. 129, fig. 115. 



1881. OHMs imgu'iformis, Davidson. ? Bi-achiopoda Budleigh-Salterton Pebble-bed, p. 347, pi. xxix, fig. 1. 

 1S83. iSti-eptorhynchus li'ipparmiyx. Hall. Second Ann. Rept. N.Y. State Geologist, pi. 39, figs. 33-36. 

 Not Oi-thls liipparUiiiyx, Schnur. 1853. Palseontographica, vol. iii, yi. 217, pi. xl, fig. 1. 

 Not Orthis Idpparionyxf, Davidson. 1865. British Devonian Brachiopoda, p. 90, pi. xvii, figs. 8-11. 



The remarkable shell described by Dr. Vanuxem as Hipparionyx proximus, so 

 far as known, is the only representative of a peculiar association of streptor- 

 hynchoid characters. The name Hipparionyx has not been in general use, 

 though, in the broad application of the generic term, which has Ijeen customary 

 in this group of shells, it should have had precedence over Streptorhynchus. 

 Schnur, in 1853, regarding what he believed to be a similar shell from the 

 Eifel as an Orthis, took the liberty of changing Vanuxem's name for the species 



* Geology of Yorkshire, vol. ii, p. 220, pi. xi, fig. 4. 1836. 



t British Carboniferous Brachiopoda, p. 127 ; British Devonian Brachiopoda, p. 81. 



