330 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Ghilotrypa Ulr. Zoaria small, ramose, witli a narrow, irregularly contracting and 

 expanding axial tnbe. Silurian to Lower Carboniferous. 



2 Ulr. (Fig. 471). Zoaria bifoliate. Oblique apertures all directed 



Meekopora eximia Ulr. 

 from the side and edge, 

 ovicell, 14/j (after Ulrich). 



Fio. 471. 



ehester Group ; Monroe Co. 

 =^4- B, Surface of same, 7/j. 



, 111. A, Specimen 

 C, Portion showinjj; 



Strotopora foveolata Ulr. 

 Keoknk Group ; Bentons- 

 port, Iowa. Part of ex- 

 pansion, 3/^, and surläce of 

 same, 7/^, showing zocecial 

 apertures and broken ovi- 

 cells (after Ulrich). 



toward the distal margin of the zoarium or branch. Liinarium moderate or obsolete ; 

 diaphragms numerous and often recurved. Ovicell rather large, showing at the 

 surface as a convex space with a small apical opening, 

 Silurian to Goal Measures. 



Strotopora Vir. (Fig. 4.1 2). Zoaria ramose. Large, abruptly 

 spreading cells (regarded as broken ovicells), distributed 

 among the zooecia on ordinary specimens; when perfectly jDre- 

 served they appear as strongly convex elevations with a small 

 opening on one side. Devonian and Lower Carboniferous. 



Lichenotrypa Ulr. First stages like Fistulipora, after 

 which large spines and irregulär thin walls are thrown up 

 about the apertures. Devonian. 



Biiskopora Ulr. (Odontotrypa, Glossotrypa Hall) (Fig. 

 473). Like Fistulipora, but lunarium remarkably de- 

 veloped, projecting ae a strong, bidenticulate process nearly 

 half across the aperture. Devonian. 



Pinacotrypa Ulr. ; (?) Botryllopora Nich. ; Selenopora 

 and Favicella Hall. Devonian ; Hexagonella W. and W. 

 Devonian and Carboniferous. 



Fig. 473. 



Buskopora dentata Ulr. 

 Devonian (Onondaga Group) ; 

 Falls of the Ohio. Portions 

 of surface, 7/ and 14/, (after 

 Ulrich). 



Order 3. TREPOSTOMATA Ulrich. ^ 



Zocecia directly superimposed upon one another so as to form long tubes intersected 

 hy straight or curved partitions (diaphragms and cystiphragms) representing the Covers 



^ Two regions of the zocecial tubes are distinguishable, an axial or " immature " region, in 

 which the diaphragms are remote, the walls thin, and the tubes prismatic through contact ; and a 

 peripheral or "mature" region, in which the tubes bend outward, the walls are thickened and 

 otherwise modified, the transverse partitions rnore abundant, and interzooecial elements (acanthopores, 

 raesopores, or mere strengtheuing tissue) are developed. 



Waagen and Wentzel aud others erroneously assert that the raesopores and acanthopores, 

 occurring so commonly in the Trepostomata, are young zocecia or " corallites. " With very few 

 exceptions, these really very different elements are not developed until the zoarium has reached the 

 niature stage, in which new zocecia cease to be given off. The origiu of raesopores {i.e. all cells 

 occupying interzocecial spaces, whether invested with separate walls or not) is due to the same 

 necessity which leads to the distal thickening of tlie zocecial tubes, namely, that of filling up space 

 occasioned by the growth of tubes at the periphery, and by the change in the direction of the tubes, 



Sonic of the tubes provisionally included under the terra raesopores, like some of the acantho- 



