PROCEEDINGS OF THE NA TIONAL MUSEUM. 



are limited to more or less imperfect remains, and when, in addition, 

 a class such as the Bryozoa requires the microscopic as well as the 

 macroscopic characters for the delimitation of species, it is not aston- 

 ishing that pioneer work in such a field should be quite imperfect. 



All of the Paleozoic systems of the North American continent, with 

 the exception of the Cambrian, afford a large number of Brj^ozoa 

 which have essentially the same general macroscopic features, but 

 which show their specific differences mainl}" upon microscopic exami- 

 nation. This applies particularl}^ to species of the order Treposto- 

 mata, or, as they have been commonly designated, the Monticuliijo- 

 rokh. Species of Trepostomata as well as of the other orders were 

 described from the external characters alone until 18T(), when Doctor 

 Nicholson published his paper Notes on the Paleozoic Corals of the 

 State of Ohio." Here for the first time the internal characters were 

 studied and illustrated by means of thin sections. This and succeed- 

 ing articles by the same writer pointed out the way for the accurate 

 stud}' of the monticuliporoids. Previous to the date mentioned, names 

 such as Chaetetes lycoperdon or C. petropolitanus were applied to 

 almost any massive paleozoic bryozoan, while Stenopora jih'osa was a 

 convenient designation for ramose forms irrespective of their geolog- 

 ical horizon. To-day the characterization of any new species, particu- 

 larly of the Trepostomata, is incomplete without the description and 

 illustration of the internal structure as well as the external features. 

 Fortunately some of the species hitherto described without a study of 

 their internal parts have such well-marked external characters that, 

 with good illustrations of the latter, it has been possible to identify 

 the species. The generic characters being in nearly all cases internal, 

 it remained for subsequent authors to properly place such species. 



Several authors have descrn)e(l a considerable number of bryozoa 

 almost entirely without illustration. In a few cases the specific charac- 

 ters are so salient that little trouble is experienced in identif3'ing the 

 species, but in the majority of cases it is impossible to do so without 

 an examination of the original t3^pes. To determine the status of as 

 many as possible of these more or less obscure species, and thus to 

 clear up the literature of the suliject, has been the endeavor of the 

 writer for some years. In the identification and final recognition of 

 such species, especially when the synonym}^ if an}", is in question, 

 one's personal equation is so liable to enter that considerable care is 

 necessary in order to obtain unbiased results. The writer has tried 

 to eliminate this element in work of this character by adhering strictl}' 

 to the rules of nomenclature. The Code of Nomenclature adopted by 

 the American Ornithologists Union (New York, 189'2) contains prob- 

 ably the best and most recent expression of the laws upon this subject, 

 and the rules employed in this paper and cited later are quoted from 

 this valuable work. 



a Ann. Mag. Nat. Hist. (4), XVIII, 1876, pp. 85-94, pi. v. 



