CLASS V 



CEPHALOPODA 



613 



pressed, and siphuncle near the venter (internal). Diifers from Phragmoceras in 

 having ajierture open throughout life. Type P. (Gyrtoceras) 

 murcliisoni (Barr.). Silurian. 



Gomphoceras Sowb. Stout short orthoceracones and 

 cyrtoceracones similar to some species of Phragmoceras, but 

 straighter, stouter and less compressed in form, and gerontic 

 aperture less contracted laterally. Hyponomic sinus 

 shorter, and curvature exogastric. Ordovician and Silurian. 



Phragmoceras Sowb. (Figs. 1136, 1137). Compressed 

 endogastric cyrtoceracones and gyroceracones, oval in 

 section, and venter narrowly rounded. Sijjhuncle large 

 and near the venter (internal). Gerontic aperture much 

 contracted laterally, the hyponomic area very long and 

 narrow. Silurian. 



Incertae Sedis. 



Fio. 1135. 



PTotcyphrcKjmoceras murcliisoni 

 (Barr.). Silurian (Etage E) ; 

 Lochkow, Bohemia. Vo- 



Nothoceras Barr. Represented by the single species N. 

 bohemicum Barrande, in which the septum turns orad, 

 forming an inverted funnel. This funnel connects with 

 a more or less inflated sheath that closed the siphuncle, and connected it with the 

 distal opening of the next succeeding septum, thus completely reversing the relative 

 positions of funnels and sheaths in other forms. The appearances as described by 



,A1^S^ 



Fig. 1136. 



Phragmoceras hroderipi Barr. Silurian (Etage E) ; Lochkow, Bohemia. 

 i/o (after Bairande). 



Fig. 1137. 



Phragmoceras loveni 

 Barr. Silurian (E) ; Loch- 

 kow, Bohemia. Section 

 showing lamellar organic 

 deposits (after Barrande). 



Barrande are not deemed sufficient to prove the truth of this statement, and it is 

 unsafe to accept it absolutely until the development has been studied. The cavity is 

 divided by radiating lamellae running longitudinally as in the Actinosiphonata. 



