MAlfUAL OF THE MOLLTJSCA. 



Type, A. Boliemicum, Barr., Pig. 5. 



Shell flask- shaped, smooth, transversely or 

 longitudinally striated, or ornamented with 

 annular folds, or plicated. The terminal cham- 

 ber (r) occupying the space above the air- 

 chambers (s), and extending down one side of 

 nearly the whole length of the shell in the 

 form of a wide and deep cavity, which is 

 Vh embraced by the decurrent edges of the in- 

 complete septa (four or five in number). This 

 cavity also communicates at its base with a 

 small siphuncle which traverses the minute 

 apical air-chambers. Aperture of shell simple. 



The wide ventral cavity of Ascoceras is of 

 the same nature as the large lateral siphuncle 

 of Cameroceras. 



Distribution, 16 species. Lower — Upper 



^'STBLmide)!''" ^^1^^^^^- Bohemia, Norway, England, Ca- 

 nada. 



Fig. 5. 



Glossoceras, Barrande, 1865. 



Etymology, glossa, a tongue, and ceras. 



Type, G. gracile, Barrande. Tipper Silurian. Bohemia. 



Shell similar to that of Ascoceras, but the dorsal margin of the 

 aperture is extended in the form of a ligulate projection, sub- 

 triangularly rounded at the end, and recurved towards the inte- 

 rior of the shell. 



This process gives rise to a distinct lobe on each side of the 

 opening, which is analogous to that which exists in Hercoceras, 

 Ophidioceras, and in certain species of Phragmoceras and Gom- 

 phoceras. 



Distribution, 2 species. Middle and Upper Silurian. Anti- 

 costi; Bohemia. 



Aphragmites, Barrande, 1865. 



Etymology, a, without phragmos, a partition ; and the usual 

 termination. 



Type, Ascoceras Buchii, Barrande. 



Shell, similar to that of Ascoceras, but the air-chambers are 

 deciduous. 



Distribution, 2 species. Upper Silurian. Bohemia. 



