﻿ULRICH-BASSLER] REVISION of paleozoic bryozoa 4' 



now that the type of structure expressed by it has turned up in the 

 Silurian faunas, we no longer hesitate in defining it. 



Genus Amplexopora Ulrich 



This genus originally included ramose species only, but we now 

 believe it advisable to extend its limits so as to include several 

 Amplexoporidce left over after the restriction of Leptotrypa to its 

 typical species and the distribution of the bulk of its species between 

 the new genera Cyphotrypa and Stigmatella. Among these unplaced 

 species are L. filiosa (D'Orbigny) and L. petasiformis (Nichol- 

 son ) which can be shown to be closely related to such typical species 

 of Amplexopora as A. septosa Ulrich (see plate xn, 10. n). 

 James' Monticulipora welshi, a subramose form or variety of L. 

 petasiformis, bridges over the gap between the two groups very 

 nicely. Leptotrypa discoidea (Nicholson) is not so easily pro- 

 vided for, we being as yet undecided as to whether it belongs to the 

 Integrata or the Amalgamata. If it is of the former type, then it 

 is still a question whether it would not be advisable to recognize 

 another genus for it. 



The propriety of referring massive as well as ramose species to 

 this genus is also confirmed by the close relations of two of the fol- 

 lowing new species, namely, A. colambiana and A. ampla. 



As to the geological range of the genus, it now appears not to ex- 

 tend beyond the top of the Ordovician. The Devonian species like 

 Monticulipora moniliformis Nicholson, that have been referred 

 here, are Amalgamata and must be provided for elsewhere. At 

 some future time we hope to discuss these in connection with the 

 rest of the Devonian Trepostomata. 



AMPLEXOPORA COLUMBIANA new species 

 (Plate XIII, 1-4) 

 Zoarium massive, generally subglobose, an inch or more in diam- 

 eter; rarely the growth is irregular, resulting in shapeless ma^e- 

 several inches in their greatest dimension. Surface without monti- 

 cules, but exhibiting maculae composed of zocecia reaching nearly 

 twice the diameter of the average cell. No mesopores. Zooecial 

 apertures polygonal, 6 to 7 of those occupying the intermacular 

 spaces in 2 mm.; walls thin, not often exhibiting the acanthopores, 

 which, in the fully matured condition, recurring at intervals during 

 the growth of a colony, are rather large, well defined, and about half 

 as numerous as the angles of junction to which they are almost 

 whollv confined. 



