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with others of the Silurian Adelphoceras and Triplooceras, which 

 also had rows of large nodes but were true nautilian shells and had 

 contact furrows. - 



The genus, Coelogasteroceras (Solenoceras), described in my 

 "Carboniferous Cephalopods," second paper, p. 447, was there 

 removed from the Rutoceratidse and placed with Coloceras under 

 the name of Coloceratidae, an error corrected in this paper. 



I also included in this family the Triassic genus Phloioceras, 

 having nautilian shells and a deep impressed zone, with Phloioceras 

 (JVaul.) gemmatum, sp. Mojsisovics, as the type and also with 

 Pleuronautilus, of Mojsisovics. 



I am strongly inclined to the opinion that the resemblances of 

 these Triassic shells to Rutoceras are superficial, but having no 

 specimens at my command I cannot make comparisons. 



Adelphoceras. 



This genus was described by Barrande in his Systeme Silurien, 

 and Adelphoceras Bohemicum the type, is a large shell with a 

 highly contracted dumbbell-shaped aperture set in the dorso-ventral 

 diameter or vertically. The outline in section is depressed kidney 

 shaped, with a shallow impressed zone, which is probably not 

 present before the whorls come in contact, or at any rate is very 

 slight at a late stage of growth, according to Barrande's figures. 



This species has a large subventran siphuncle and there are three 

 rows of tubercles on either side, and it is obviously closely related 

 to Triplooceras, but is remote from Hercoceras, as is demonstrated 

 by the aperture form ornaments and lines of growth.* 



Triplooceras. 



This genus, described in Genera of Fossil Cephalopods, is 

 obviously closely related to Adelphoceras, having three rows of 

 tubercles on either side, but the form is more highly developed, 

 being a depressed oval and the coiling closer with a deeper contact 

 zone and the ornaments disappear much earlier on the shell. It is 

 obviously a grade more progressive than Adelphoceras, but in the 

 same genetic group. 



Besides Triplooceras (Naitf.) inspiration, sp. Barrande, PI. 

 "461," there is Triplooceras (Troch.') reliquum, sp. Barrande, PL 



* Barrande's Adelphoceras secundum is here referred to Hercoceras. 



