330 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



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

 expanding axial tube. Silurian to Lower Carboniferous. 



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



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f 







j» * ^ «■ 



i 



^ 



tki^:mJ& 



Pio. 471. 



A M 



Meekopora cximUi Ulr. Chester Group; Monroe Co., 111. A, Specimen 

 from the side and edge, -Vj- />', Surface of same, "iji. (', Port-ion showing 

 ovicell, w/j (after Ulrich). 





IP * • 



«..• 



i 





Fi(i. 472. 



Strtitopora fofcolatu Ulr. 

 Keokuk Group ; Bentons- 

 port, Iowa. Part of ex- 

 pansion, 3/^, and surface of 

 same, "i/i, showing zofHcial 

 apertures and broken ovi- 

 cells (after Ulrich). 



toward the distal margin of the zoarium or branch. Lunarium 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 Coal Measures. 



Strotopora Ulr. (Fig. 472). Zoaria ramose. Large, abruptly 

 spreading cells (regarded as broken ovicells), distributed 

 among the zocecia on ordinary specimens; when perfectly pre- 

 served they appear as strongly convex elevations with a small 

 opening on one side. Devonian and Lower Carboniferous. 



Lichenotrypa Ulr. First stages like Fisttdipora, after 

 which large spines and irregulaj' thin walls are thrown up 

 alwut the apertures. Devonian. 



Buskopora Ulr. {Odontotrypa, Glossotrypa Hall) (Fig. 

 473). Like Fistulipora, but lunarium remarkably de- 

 veloped, projecting as a strong, l)identiculate process nearly 

 half across the ajjerture. Devonian. 



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

 Devonian ; Hexagonella W. and W. 





Fig. 473. 



Buskopora dentata Ulr. 

 Devonian (Onondaga Group) ; 



Falls of the Ohio. Portions and Favicella Hall 

 of .surface, 7/ and ^Vl (after -p, . i /-. , -p 



Ulrich). Devonian and Carbonnerous. 



Order 3. TREPOSTOMATA Ulrich. ^ 



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

 by straight or curved partitions {diaphragms and cystiphragms) representing the covers 



^ Two regions of the zooecial tubes are (li.stiuguishaljle, an axial or " immature " region, in 

 which the diaphi-agms 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 ai-e thickened and 

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

 mesopores, or mere strengthening tissue) are developed. 



Waagen and Wentzel and others erroneously assert that the mesopores and acanthopores, 

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

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

 mature stage, in which new zooecia cease to be given off. Tlie origin of mesopores {i.e. all cells 

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

 necessity wliich leads to the distal thickening of tlie zorecial tubes, namely, that of filling up space 

 occasioned by the growtli of tubes at the jjeriphery, and by the change in the direction of the tubes. 



Some of the tubes provisionally included under the term mesopores, like some of tlie acantho- 



