Ruth R. Mook — A New Cephalopod. 617 



Akt. XLII. — A New Cephalopod from the Silurian of 

 Pennsylvania ; by Ruth Raedek Mook. 



Introduction. 



DuRiNa the summer of 1913 while working on the Blooms- 

 burg Red Shale and the overling limestones, in a limestone 

 quarry about 7 miles southwest of Bloomsburg, Pennsylvania, 

 the writer's attention was called to a rare cephalopod col- 

 lected and owned by Mr. Guy A. Mowry of Grovania. The 

 specimen was first discovered by quarry men while excavating 

 rock to be sent to the lime kilns. Mr. Mowry, who has care- 

 fully collected fossils for some years, was called in to make a 

 careful note of the exact position and horizon of the specimen. 

 The fossil was found in a bed of limestone, generally known 

 in eastern Pennsylvania as the Bossardville, of Upper Silurian 

 age. 



So far as can at present be determined, a similar form has 

 not yet been described for the United States, and because of 

 its apparent rarity it has seemed worth while to call attention 

 to it. Mr. Mowry has therefore kindly loaned the specimen 

 for the purpase of description. 



The name Trochoceras grovaniense is here proposed for this 

 new species. 



The genus Trochoceras. 



The genus Trochoceras was proposed without any concert of 

 action by Barrande in 1848 and Hall in 1852 for fossil species 

 generically similar but not generically identical. At a meet- 

 iug of the " Freunde der Naturwissenschaften in Wien," on 

 September 10th, 1847, Dr. Franz v. Hauer called the attention 

 of the members to some new cephalopods from the Silurian of 

 Bohemia, which had been sent in by Barrande. The proceed- 

 ings of this meeting were published in 1848.* The report 

 included Barrande's original description of the genus Trocho- 

 ceras, which reads as follows : 



" Trochoceras (Barrande). The shell is characterized by the 

 peculiar nature of its enrollment. The revolutions are laid 

 upon one another in a spiral manner, so that the shell itself is 

 not symmetrical. Trochoceras parallels therefore the genus 

 Turrilites in the family of the Ammonitidae. All the species 

 which Barrande discovered belong to the lower division of the 



* Berichte liber die Mittheilungen von Freunden der Naturwissenschaf ten 

 in Wien ; gesammelt und herausgegeben von Wilhelm Haidinger, iii, Nr. 

 1-6, p. 264, July-December, 1847. Vienna, 1848. 



