14 
PALEONTOLOGY OF NEW YORK. 
rad, from the Lower Helderberg group. Though this type is not abundantly 
developed in American faunas it embraces a very considerable number of the 
many forms described by Barrande* from the Bohemian etages E and F. 
Among these species the cardinal area has but an incipient development or may 
be altogether absent, while the dental plates are frequently quite pronounced. 
2. Multiplicati, or those with numerous plications; as Spirifer Niagarensis, 
Conrad, S. asperatus, Ringueberg, of the Niagara group ; S. TuUia, Hall, of the 
Hamilton fauna; S. Belphegor, Clarke, of the Genesee shales; S. mesastrialis, 
Hall, of the Chemung group. In this group, with the more extended hinge 
and more abundant plications characterizing the Devonian and Carboniferous 
Spirifers generally, the radiate type of superficial structure has been maintained 
the longest. It is evident from material before us, that the type was continued 
into the faunas of the Lower Carboniferous. 
3. DuplicAplicati. A few upper Silurian species have strong dichotomous 
plications and the filamentous surface striae covered with asperities. Such are 
Spirifer nohilis, Barrande, from the etage E 2 , and the Niagara limestone of 
Illinois and Wisconsin, and S. Schmidti, Lindstrom, from the Gotland lime¬ 
stone. 
The Radiati generally may be said to have prevailed at an early period in 
the history of the genus. The combination was one that was but little modi¬ 
fied during its existence and was involved in no progressive development of 
generic characters. 
II. Lamellosi. Typical examples, Spirifer perlamellosus, Hall, S. mucronatus, 
Conrad. 
(2a) 1820. Terebratula, Atwater. Amer. Jour. Sci. and Arts, vol. ii, p. 224, pi. i, figs. 2, 3. 
(2a) 1841. Delthyris, Corrad. Geol. Sui-vey N. Y., Pal. Dept.. ; Fifth Ann. Kept., p. M. 
(1) 1842. Delthyris, Conrad. Jour. Acad. Nat. Sci. Philadelphia, vol. viii, pp. 261, 262, pi. xiv, fig. 18. 
(1) 1842. Delthyris, Vanuxem. Geology of N. Y. ; Kept. Third Dist., j-). 132, fig. 3. 
(2a) 1842. Delthyris, Vanuxem. Geology of N. Y. ; Kept. Thii-d Dist., p. 150, fig. 3. 
(1) 1843. Delthyris, Hall. Geology of N. Y. ; Kept. Fourth Dist., p. 105, fig. 4; p. 200, fig. 5; 
pp. 202, 269, fig. 9 ; p. 270, fig. 5. 
(2a) 1843. Delthyris, Hall. Geology of N. Y. ; Kept. Fourth Dist., p. 198, figs. 2, 3 ; p. 205, fig. 32; 
p. 270, fig. 3. 
(2a) 1843. Spirifer, Castelnau. Essai sur le Systems Silur. de I’Amer. Septentr., pi. xiii, fig. 1. 
* Sysieme Silurien du Centre de la Bohenie, vol. v, i)Is. i-viii. 
