194 



MAirCAL OF THE MOLLUSCA. 



Shell, like a curved gomphoceras ; sipliuncle external. 

 Distrihutiony 3 species. Silurian, New York. 



Pheagmoceras, Broderip. 



Etymology, pliragmos, a partition, and ceras, a horn. 



Type, P. ventricosum (Steininger species), PL II., Pig. 15. 



Shell curved, laterally compressed ; aperture contracted in the 

 middle ; siphunde, ventral, radiated. Example, P. caUietoma, 

 Bar., Fig. 48. 



Distrihution, 15 species. Lower Silurian — Carb. ; Brit., 

 Germany. 



Cyetoceeas, Goldf., 1832. 



Etymology, curios, curved, ceras, horn. 



Synonyms, Campulites, Desh., 1832 (including gyroceras). 

 Aploceras, D'Orbigny. Campyloceras and trigonoceras, McCoy. 

 Gyroceras, D'Orbigny. 



Example, 0. hybridum, Yolborthi, andBeaumonti (Barrande). 



Shell curved ; siphunde small, internal, or sub-central. 



Fossil, 84 species. Lower Silurian — Carb. ; North and South 

 America and Europe. 



Fig. 59.* 



Gyeoceras, Meyer, 1829. 

 Etymology, gyros, a circle, and ceras. 

 Synonym, NautUoceras, D'Orbigny. 



Example, G. eifeliense, D'Arch. (PL IL, Fig. 13). Devonian; 

 Eifel. 



* Fig. 59. Gyroceras Goldfussii. {— omatum Goldf.). &, siphunde cf G. depressum, 

 Goldf. sp. Devonian, EifeU From MM. D'Ai'chiac and YprneuLl. 



