ORDER IT 



CYCLOSTOMATA 



327 



families Ceramopoiidae and Fistuliporidae, wliicli were formerly assigned to the 

 Trepostomata and latterly to the Cyclostoniata. They agree with the Trepostomata 

 in having well-defined immature and mature zones but their minutely porous walls 

 of irregiilarly laminated tissue, large mural communication pores and finally, ooecia 

 tyi^ical of the Cyclostoniata seem to ally them more closely with the latter order. 

 This suborder is possibly the Paleozoic representative of the Cerioporina. 



Family 16. Ceramoporidae Ulrich. 



Zoaria variable; maculae or clusters of mesopores and of zooecia, larger than the 

 average, occnr at regular intervals. Zocecial apertures usually oblique, of sub-triangular, 

 ovate or polygonal form; lunarium present, appearing at the surface as a prominent 

 overarching hood, or as a slightly elevated portion of the margin, of crescentic form 

 ivith the ends projecting more or less into the aperture. Mesopores or interstitial cells 



Via. 461. 



a, Ceramopora spongiosa Bass. Tangential section, 20/j. b, c, AnoloticMa rhmnUca Bass. Vertical sections 

 showing mural pores, 20/i. d, Crepipora incraaxata Bass. Vertical section with ovicell-like structures, lO/i 

 (after Bassler). 



generally present, always irregular, and usually without diaphragms. A few horizontal 

 diaphragms often present in the zocecial tubes. Walls minutely porous, composed of 

 intimately connected and irregularly laminated tissue. Large mural commAinication 

 pores sometimes present. Ordovician to Devonian. 



This is one of the largest and most important of the families of Paleozoic Bryozoans, and 

 is especially common iu the Middle and Upper Ordovician. The 

 earliest forms resemble Bercnicca and Apsendesia ; while Ceramo- 

 porella, Chiloporella, and especially FavositcUa, may be regarded 

 with reasonable confidence as tbe progenitors of the Fistuliporidae. 

 At any rate the connection between the two families is so intimate 

 as to forbid any wide separation. 



Ceramopora Hall (Fig. 461, «;. Discoidal, free, lamellate, 

 massive or parasitic. When free, under surface with one or 

 more layers of small irregular cells. Zooecia opening on the 

 upper surface, large, irregular, oblique, imbricating, and radially 

 arranged about the dep)ressed centre. Mesopores irregular, short, 

 numerous. Large communication pores in walls of both zocecia 

 and mesopores. Ordovician to Devonian. 



Geramoporella Ulr. (Fig. 462). Zoaria encrusting, 

 tubes short, walls thin, apertures more or less oblique, hooded, 

 commonly of oval shape. Mesopores abundant, often completely isolating the zooecia, 

 Ordovician and Silurian. 



Fio. 462. 



Ceramoporella distiiicta 



Ulrich. Lower Trenton, 



Minne.sota. Surface of para- 



Zocecial fl^ic expansion, I'^/j (after 



Ulrich). 



