MORPHOLOGICAL DIFFERENTIA TION. 



331 



Fig. ioi.—Orth(t- 

 cerai titniduiH 

 Barr. 



Fig. lo^. — CyrtOit-tiis Murchi- 

 soni Barr. 



Fig. 105. — Hamitet 

 rotundus Sow. 



J^ig. 106. — Gyroceras alatum Barr. 



Fig. 107.- Tri\hocerns ,^/'t,itum Barr. 



