46 [Senate ' 



An examination of Professor Locke's description and drawings 

 will at once determine that his trilobite is not a ceraurus, but 

 must either be placed in the genus Jicidaspis of Murchison, or 

 Odontopleura of Emmrich; both of which may be regarded as 

 synonyms, as the characteristics of either genus will cover the 

 specimen. 



The question then occurs, Shall the genus of Murchison or 

 Emmrich be adopted? M. Barr'ande has proved that Murchi- 

 son's name has priority in regard to time; this fact decides the 

 question in favor of Murchison. I also prefer the name of Mur- 

 chison, for the following additional reasons : 



1st. Professor Timothy A. Conrad, the Palaeontologist to the 

 New-York survey, was the first American author who adopted 

 Murchison's genus; and in his annual report on the palaeon- 

 tology for the year 1839 (third report, pa, 204), describes a true 

 Jicidaspis (^Jicidaspis tuberculatus) as occuring in the Delthyris 

 Shaly limestone; which is the first notice of the occurrence of 

 Murchison's genus on the western continent. 



2d. Professor James Hall, the present State Palaeontologist j 

 adopts Murchison's genus; and in volume 1 of the New-York 

 Palaeontology, pa. 240, describes a trilobite as the Acidaspis 

 trentonensis^ from the rock formation at the Bay of Quinte on 

 Lake Ontario, which, from its associated fossils, he considers 

 equivalent to the Trenton limestone. 



3d. Professor Shumard, the Palaeontologist of Missouri, also 

 adopts Murchison's generic name; and in the second annual 

 report of the geological survey of Missouri (1854), part 2, pa. 

 200, describes a new species, Acidasfis halli (in honor of Pro- 

 fessor Hall), from the Cape Girardeau limestone, which the 

 geologists of Missouri consider as belonging to Murchison's 

 Upper Silurian system, and to the lower Helderberg group of 

 the New-York geologists. 



Adopting the genus of Murchison, I therefore propose for 

 Professor Locke's specimen the name of Acidaspis crosotus, 

 Locke; retaining Professor Locke's specific name of crosotus 

 (from the Greek word signifying fringed), as descriptive of the 

 fossil, and in accordance with the established rules of scientific 

 nomenclature. G. 



