ISO.] 



CRUSTACEA. 



551 



americanus, Billings, 1859, Can. Nat. and 



Geol., vol. 4, p. 371, Trenton Gr. 

 angusticollis, Billings, 1859, Can. Nat. and 



Geo., vol. 4, p. 376, Black Riv. Gr. 

 arcturus, Hall, 1847, Pal. N. Y., vol. 1, p. 



23, Chazy and Black Riv. Grs. 

 arcuatus, Billings, 1865, Pal. Foss., vol. 1, 



p. 279, Quebec Gr. 

 armatus, Hall, 1867, 20th Rep. N. Y. St. 

 , Mus. Nat. Hist., p. 418, Niagara Gr. 

 barriensis, Murch. 1839, Sil. Syst. The 



species formerly identified with this is 



Illtenus ioxus. 

 bayfieldi, Billings, 1859, Can. Nat. and 



Geo., vol. 4, p. 369, Chazy Gr. 

 clavifrons, Billings, 1859, Can. Nat. and 



Geo., vol. 4, p. 379, Chazy and Black 



Riv. Grs. 

 conifrons, Billings, 1859, Can. Nat. and 



Geo., vol. 4, p. 378, Black Riv. Gr. 

 conradi, Billings, 1859, Can. Nat. and 



Geo., vol. 4, p. 372, Black Riv. Gr. 

 consimilis, Billings, 1865, Pal. Foss., vol. 



1, p. 277, Quebec Gr. 

 consobrinus, Billings, 1865, Pal. Foss., vol. 



1, p. 280, Quebec Gr. 

 cornigerus, Hall, 1872, 24th Rep. N. Y. 



St. Mus. Nat. Hist., p. 186, Niagara Gr. 

 crassicauda, Wahlenberg, 1821, (Ento- 



mostracites crassicauda,) Nov. Act. Soc. 



Upsal., vol. 8, p. 27, and Pal. N. Y., 



vol. 1, p. 229, Trenton and Galena Grs. 



Fig. 1015.— Illsenu's globosus. Two views. 



cuniculus, Hall, 1867, 20th Rep. N. Y. St. 



Mus. Nat. Hist, p. 421. Niagara Gr. 

 daytonensis, Hall & Whitfield, 1875, Ohio 



Pal., vol. 2, p. 119, Niagara Gr. 

 fraternus, Billings, 1865, Pal. Foss., vol. 1, 

 p. 276, Quebec Gr. 



globosus, Billings, 1859, 



Can. Nat. and Geo., 



vol. 4, p. 367, Chazy 



Gr. 



graftonensis, Meek & 



Worthen, 1869, Proc. 



Acad. Nat. Sci. Phil. 



and Geo. Sur. 111., vol. 



6, p. 508, Niagara Gr. 



grandis, Billings, 1859, 



Can. Nat. and Geo., vol. 4, p. 380, Hud. 



Riv. Gr. and Mid. Sil. 



herricki, Foerste, 1887, 15th Rep. Geo. and 



Nat. Hist, of Minn., p. 479, Trenton Gr. 



imperator, Hall, 1861, Rep. of Progr. 



Wis., p. 49, and 20th Rep. N. Y. St. 



Mus. Nat. Hist., p. 332, Niagara Gr. 



incertus, Billings, 1865, Pal. Foss., vol. 1, 



p. 332, Quebec Gr. 

 indeterminatus, Walcott, 1877, 31st Rep. 

 N. Y. St. Mus. Nat. Hist., p. 70, Black 

 Riv. Gr. 



Fig. 1016.— lllsenus 

 globosns. Side 

 view. 



insignis, Hall, 1864, 20th Rep. N. Y. St. 



Mus. Nat. Hist., p. 331, Niagara Gr. 

 ioxus, Hall, 1867, 20th Rep. N. Y. St. 



Mus. Nat. Hist., p. 420, Niagara Gr. 

 latidorsatus, Hall, 1847, Pal. N. Y., vol. 1, 



p. 230, Trenton Gr. 

 madisonanus, Whitfield, 1882, Geo. Wis., 



vol. 4, p. 307, Niagara Gr. 

 milleri, Billings, 1859, Can. Nat. and Geo., 



vol. 4, p. 375, Black Riv. and Tren- 

 ton Grs. 

 minnesotensis, Foerste, 1887, 15th Rep. 



Geo. and Nat. Hist, of Minn., p. 478, 



Trenton Gr. 

 niagarensis, Whitfield, 1880, Ann. Rep. 



Geo. Sur. Wis., p. 68, Niagara Gr. 

 orbicaudatus, Billings, 1859, Can. Nat. and 



Geo., vol. 4, p. 379, Hud. Riv. Gr. and 



Mid. Sil. 

 ovatus, Conrad, 1843, (Thaleops ovatus,) 



Proc. Acad. Nat. Sci. Phil., vol. 1, p. 



332, and Pal. N. Y., vol. 1, p. 259, Black 



Riv. Gr. 

 pterocephalus, Whitfield, 1878, Ann. Rep. 



Geo. Sur. Wis., p. 87, and Geo. Wis., 



vol. 4, p. 309, Niagara Gr. 

 simulator, Billings, 1865, Pal. Foss., vol. 1, 



p. 327, Quebec Gr. 



Fig. 1017.— Hideous taurus. 



taurus, Hall, 1861, Rep. of Progr. Wis. 

 Sur., p. 49, and Geo. Sur. 111., vol. 3, p. 

 320, Trenton and Galena Grs. 



trentonensis, Emmons, 1842, (Bumastus 

 trentonensis,) Geo. Rep. N. Y., p. 390, 

 and Pal. N. Y., vol. 1, p. 230, Tren- 

 ton Gr. 



tumidifrons, Billings, 1865, Pal. Foss., vol. 

 1, p. 278, Quebec Gr. 



vindex, Billings, 1865, Pal. Foss., vol. 1, p. 

 179, Chazy Gr. 



worthenanus, syn. for Illsenus insignis. 

 Isochilina, Jones, 1858, Can. Org. Rem., 

 Decade 3, p. 197. [Ety. isos, equal; 

 cheilos, lip.] Equivalve, the margins of 

 the valves meeting uniformly, not over- 

 lapping, as in Leperditia greatest con- 

 vexity central or toward the anterior 

 end, eye tubercle present; muscular 

 spot not distinct, externally. Type I. 

 Ottawa. 



