CRUSTACEA. 13 



the outline and contour usual in this part of Bronteus. It may, therefore, 

 with propriety, be regarded as belonging to this species. 



Observations. This species is represented only by the two fragments 

 described, both of which were discovered by Professor S. (•. Williams, of Cor- 

 nell University, by whose kindness this notice appears. Unusual interest 

 attaches to it as the first representative of the genus Bronteus discovered in 

 the Devonian of America, although the genus is abundantly represented in 

 the Devonian horizons of Europe. A dose relationship is observable in the 

 species Bronteus Tullius and B. granulatus, Goldfuss, from the middle Devonian 

 of the Eifel and the lower upper-Devonian limestone of the [berg-Winterberg 

 terrane. This similarity consists in the number and contour of the ribs and the 

 ornamentation of the dorsal surface and doublure. The fauna of the Iberg lime- 

 stone is characterized by a vcvy abundant development of the species Rhyn- 

 chonella cuboides, Sowerby, of which species the American representative R, 

 venustula, Hall, occurs only in the Tully limestone, the formation from which 

 Bronteus Tullius has been derived. The row of minute spinules along the pos- 

 terior margin of the pygidium of our species shows its relationship to the 

 comparatively limited group of forms following the type of Bronteus thysanopeltis, 

 Barrande. This group includes at present the following species, viz.: B. thysa- 

 nopeltis, Barrande, B. Clementinas, Barrande, B. acanthopeltis, Schnur, />'. Barrandii, 

 Hebert, B. Waldschmidti, von Kcenen, B. Raphaeli and B. Trutati, Barrois, 

 and B. Tullius. In Bronteus Tullius these spines are much more minute than in 

 any other of the species mentioned. Kayser* has observed that this group of 

 Bronteus stands in the same relation to the Silurian forms of the genus as the 

 genus Cryphceus does to the normal forms of Dalmaniles, i.e., those after the 

 type of D. Hausmanni. So far as known, it is limited to Devonian faunas, and 

 is appropriately designated by the term Thysanopeltis, applied to this variation 

 by Corda (Prodrom. Monog. Trilob., 1847), and revived by Barrois (Ann. de la 

 Soc. Geol. du Nord, p. 131, 1886), with sub-generic value. 



Distribution. Hamilton group. In the Tully limestone, Kingsley's Hill, north- 

 east of Otisco, and Borodino, Onondaga county. 



*J31teste Devon- Ablag des Harzes, p. 255. 1878. 



