SECONDARY AND TERTIARY FORMATIONS OF NORTH AMERICA. 113 



C. One special pore to each cellule. 



a. In advance of the opening, EscKannellidd 



* Subfamilies as above, Escharinellince and Porellince. 



b. Behind the opening, Fbrinidce. 



* Subfamilies Porininai and PorellinincB. 



D. Two or more pores around the opening, . . EscharelUndce. 



* Subfamilies Escharellininas and Eschariporince. 



E. Cellules composed of two chambers or stages superposed, Steginoporidce. 

 II. Celhdata opercidata. 



A. Without special pores, . .... Flustrellarklce. 



B. One pore behindf the opening, Flustrellidce. 



C. Two pores, (or more), Fhistrinidce. 



This classification is somewhat different from the modification proposed by Pictet> 



which has the appearance of having been founded only on the study of d'Orbigny's 

 book, and not on experience in studying specimens, the only true way of obtaining 

 a knowledge of any science. We wish to be understoood that, while we consider the 

 above arrangement far preferable to d'Orbigny's, we do not claim for it exemption 

 from perhaps grave objections, to be modified by future experience. It must be 

 remembered that the study of the Polyzoa is still in its infancy. It has only been 

 within a few years that the true relations of these little beings have been determined, 

 and little more than ten years have elapsed since the first important attempt was 

 made to arrange them. Since then but two or three students have paid any con- 

 siderable attention to them. 



D'Orbigny studied them only with reference to the fossil species, and his arrange- 

 ment of the corneous forms is eminently artificial; while other authors have paid 

 little comparative attention to the fossils, thereby losing perhaps many important 

 links which might be of great importance in connecting allied forms. 



In regard to the classification of the Centrifuginates, we are not at all satisfied that 

 the three divisions of d'Orbigny— the fasciculates, the tubulates and the foraminates— 

 should not be united, as suggested by Pictet, under the name of " Tabid iporides." 

 Many of the tubulates, for instance, those of the family " Tuhigeridce," have a dis- 

 tinctly grouped arrangement, as in the genera Idmonea, &c. ; and among the forami- 

 nates there are several instances in which the cellules of certain species are fully as 

 exsert as some of the tubulates. The cellules of Multicrescis Ricordeana, for example, 

 as figured by d'Orbigny, are as prominent as those of our Diastopora lineata. We have 

 not had an opportunity of studying this portion of the subject as fully as we could 



t Our species Reptoflustrella? heteropora is either an exception to this rule, or should probably be con- 

 sidered the type of a new genus and family, the analogue of the Eschar innUkh<- among the non-opcrculates. 



