344 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Neviat axis HsiW. Devonian. Nemafotry2M ^a^Bulev. Ordovician. Orthojyora }ia.]]. 



Fig. 503 



a, (.'iielocnnuf: rhomhtciiji Ulr. Vi and surface i-/]. h, Rh(wibripora inonissatii Ulr. i/j anil "^/j. c, Strehlotrypa 

 major Ulr. i/i and is/j. d, Amnthodema conjiue.ns Ulr. i/i and --i/i (after Uliicli). 



Silurian and Devonian. Hyphasmopora Etlieridge. Carbonifei-ous. Acanthoclema 

 Hall (Fig. 503, d). Silurian to Lower Carboniferous. 



Trofidopora Hall. Devonian. Strehlotrypa Ulrich (Fig. 503, c). Devonian and 

 Lower Carboniferous. 



Family 6. Ptilodictyonidae Ulricli. 



Zoaria bifoliate, composed of two layers of zooxia groivn together back to hack, usually 

 joined at least at the base, and forming leaf-like expansions, or comjjressed, branching 

 or inosculating stems. Mesial plates without median tihbuli ; hemisepta usually present. 

 Inner orifice generally semi-elliptical, the outer more rounded, usually ovate, and 

 surrounded, by either a slopiing area or ct ring-like peristome. Vestibules separated by 

 thick walls. Ordovician to Devonian. 



Ptilodictya Lonsd. (Heterodictya Nicli.). Zoaria lanceolate or falciform, with a 

 small basal eximnsion. In the young condition the zoariuni consists of longitudinally 

 arranged, narrow, olilong-quadrate zorecia, new zooccia, of different width and arrange- 



a. 



W 









^e^) 

 ^ 



"*^»^^e ^ 



Fn:. 504. 



a, Esi-liaropovd anguluris IJlr. l/i and surface i'/i- '', E. suhrerta Ulr. "/j. (■, </, Stictojiorella criljmm Ulr. l/j 

 and surface i8/j. Black River of Minnesota (after Ulrich). 



nient, being added subsequently on each side. In the vestibulai' or outer region the 

 walls are more or less thickened, solid, and with a double row of exceedingly minute 

 dots. Silurian and Devonian. 



