GEOLOGY AND MINERALOGY. 491 



CIENTIEIC AND LITEEAET NOTES. 



GEOLOGY AND MINERALOGY. 



NEW AMERICAN TEILOBITES : BY PROFESSOR JAMES HALL. 



The accompanying descriptions of three new Trilobites from the Hudson River 

 group of Vermont, have been liiudly forwarded to us by Professor Hall, of Albany : 



" The Trilobites most common in the shales of the Hudson River Group are 

 Triarthrus Bechii* and Calymene senaria — C. Blumenbachii ? I have likewise 

 described two species of Olenus in the first volume of the Palaeontology of New 

 York; but these are rare in most localities of the rocks of this period. 



Some years since, during the progress of the Geological Survey of Vermont, by 

 Rev. Z. Thompson, some specimens of Trilobites were obtained from the shales of 

 this age in the town of Georgia; and these were subsequently placed in my hands. 

 The Survey having since passed under the direction of Professor Hitchcock, I post- 

 poned the publication of the descriptions, fearing it might not be agreeable to him ; 

 but having now not only his approval, but his express desire that I would publish 

 them, I give below the following species, preliminary to a more complete descrip- 

 tion and illustration. 



Olenus Thompsoni. {n. s.) 



General form ovate, the length and breadth being nearly as sis to five. Head 

 broad lunate, with the postero- lateral angles much extended ; the width from the 

 centre to the outer margin of the eye almost equal to the width of the cheek. 

 Eyes (which are much crushed in the specimen) elongate semioval, equal in length 

 to the space between the anterior angles and the frontal margin : glabella dis- 

 tinctly lobed, narrower in front. 



Thorax with the lateral lobes about once and a half as wide as the middle lobe, 

 consisting of fourteen articulations, the third one of which is much longer than the 

 others, and curving downwards with an extension reaching as far as the line of 

 articulation of the seventh rib. The posterior articulations are bent abruptly 

 backwards, so that the free extremities are parallel with the axis. Pygidium 

 small, pointed, without visible rings, and having a narrow ridge running down the 

 centre. 



The description is chiefly drawn from an impression in slate, and a cast made 

 from the same, together with some fragments of the same species. 



Geological position. — In the shales in the upper part of the Hudson River group. 



Olenus Vermontana. {n. s.) 



General form elongate ; the posterior extremity obtuse. Head semioval, twice 

 as wide as long, the posterior angles produced in short acute spines. Eyes nar- 

 row elongate ; the space from the centre of the head, to the outer margin of the 

 eye much greater than the cheek, and the distance from the anterior angle of the 



* Apparently confined (or nearly so,) in Canada, to the underlying Utica Slate.— E. j. c. 



