262 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vOL. 45 



register of American species in his American Geology and Paleontol- 

 ogy, 1898, and similar treatment of Vinella in the Supplement pub- 

 lished three years later, likewise add nothing new to the subject. 



The above references, it is believed, constitute a complete historical 

 sketch of the subject. As we describe, or at least make critical 

 remarks about every known species, and, with few exceptions, give 

 one or more figures of each, this work might perhaps justly claim 

 the rank of a monograph. However, we are far from claiming any 

 such dignity for our effort, its aim being no higher than the produc- 

 tion of something that might prove a useful basis for further investi- 

 gations. 



It should be stated in this connection that we know little about 

 these fossils, and while their classification with the Ctenostomata 

 is perhaps a little better than a mere working theory, it rests mostly 

 on highly suggestive resemblances between the incomplete fossil 

 organisms and the supposed corresponding parts of living forms, 

 and upon conjectures as to the unknown parts. Still, whatever 

 position may ultimately be assigned to them, it seems certain that 

 their reference to the Ctenostomatous Bryozoa is at present opposed 

 by fewer objections and at the same time supported by more and 

 stronger agreements than appear when they are compared with any 

 other class of organisms. 



The only objection that might be considered valid is the difference 

 between the chemical constituents of the zoarium of the recent 

 Ctenostomata and their supposed Paleozoic ancestors. In the 

 former the zoarium is either horny or membranaceous, and in many 

 cases perhaps quite incapable of preservation in the fossil state. In 

 the ancient types, on the contrary, the zoarium, though not by any 

 means so calcareous as in other types of Bryozoa, nevertheless con- 

 tained enough hard and resistant matter to render them capable of 

 fossilization. In some the preservation is generally good, in others 

 rarely satisfactory, while all exhibit unmistakable differences in the 

 composition of their zoaria when compared with associated similarly 

 adnate but purely calcareous zoaria of Cyclostomata like Stomato- 

 pora. Unfortunately we are unable to say what these differences 

 consist of, but we have no reason to doubt that they are of kinds 

 comparable with those existing between recent Cyclostomata and 

 Ctenostomata. 



Of the various forms referred to here as Paleozoic Ctenstomata, 

 none, with the possible exception of Rhopalonaria, is known by its 

 zooecia. Assuming provisionally that the fusiform swellings of 

 Rhopalonaria are really the zooecia, we are at once confronted by 



