519 
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 Rutoceratidz and placed with Coloceras under 
the name of Coloceratidz, 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 Phlococeras 
(Naut.) 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 Systéme 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 Zyriplooceras (Naut.) inspiratum, sp. Barrande, Pl. 
*¢461,’’ there is Zriplooceras (Troch.) reliquum, sp. Barrande, PI. 
* Barrande’s Adelphoceras secundum is here referred to Hercoceras. 
p 
