112 PALEONTOLOGY OF NEW YORK. 



purpose to distinguish the earlier forms possessing such characters by a sep- 

 arate name. 



The term Homckospira is suggested, and the division will at present include 

 Retzia evax, Hall, Retzia apriniformis, Hall, and Retzia sobrina, Beecher and Clarke; 

 all of the Niagara fauna. 



Genus PTYCHOSPIRA, gen. nov. 



FLATS L. 



1884. TerAratala, von Bdch. Ueber Tei-ebrateln, p. 76, pi. ii, fig. 37. 



1841. Terebralula, Phillips. Pal. Foss. Cornwall, Devon and West Somei-set, p. 89, pi. xxxv, fig. 163. 



1841. Tertibratvla, d'Abchuc and db Vbrmeuil. Trans. Greol. See. London, second ser., vol. vi, p. 368, 



pi. XXXV, fig. 3. 



1849. Spirigerina, d'Orbiqht. Prodrome de Palcontologie, vol. i, p. 100. 



1853. Terebratula, Schnur. Palspontogi-aphica, vol. iii, p. 184, pi. xxv, fig. 4. 



1855. Retzia, Thb Samdbbbobrs. Verstein. der rhein. Schicht. Syst. in Nassau, p. 330, pi. xxxii, fig. 13. 



1862. Retzia, Whitb and Whitfield. Pi'oc. Boston Soc. Nat. Hist., vol. viii, p. 294. 



1863. Retzia. Hall. Sixteenth Ann Kept. N. Y. Slate Cab. Nat. Hist., pp. 66, 57, figs. 4-6. 



1864. Retzia, Davidson. British Devonian Brachiopoda, p. 21, pi. iv, figs. 8-10. 



1871. Retzia, Qoenstbdt. Petrefacktenkunde Deutschl. ; Brachiopoden, pp. 433, 434, pi. li, figs. 10-14. 

 1871. Retzia, Katsbr. Zeitschr. der deulsch. geolog. Qesellsch., vol. xxiii, pp. .557, 558, ]il. x, fig. 5. 

 1882. Retzia, Davidsoit. British Devonian Brachiopoda, Supplement, p. 29, pi. i, figs. 30, 31. 



Among the species currently referred to the genus Retzia are a few which 

 possess a very different exterior from the typical forms of all the retzioid 

 genera here discussed. Certain of these fall into a natural group on the basis 

 of a very coarsely and sparsely plicated surface, and to this group it is pro- 

 posed to apply the above designation; it will include the Terebratula ferita, 

 von Buch, Retzia longirostris, Kayser, both of the Eifel middle Devonian, and 

 the R. sexplicata, White and Whitfield, of the Kinderhook group. 



In Terebratula ferita, which is taken as the typical representative of this division, 

 the surface of each valve bears seven radial plications, which are sharply angular 

 and greatly elevated at the margins of the shell. The median plication on the 

 brachial valve is usually divided by a fine sulcus, there being a corresponding' 

 ridge in the .sinus of the opposite valve. The beak of the pedicle-valve is erect, 

 and truncated obliquely by a circular foramen, beneath which lies a flat deltidium, 

 the plates of which are, as in allied genera, more or less completely coalesced. 

 The epidermal layer of the shell is finely pitted, the punctations apparently not 



