BRYOZOA. 365 



points of resemblance. The relationship to Stenopora would 

 scarcely be even suggested by a comparison between the typical 

 species of that genus and of Rbombopora, yet, when the com- 

 parison is extended to a large number of species, it becomes 

 clear enough. For instance, Stenopora ramosa and Rhombo- 

 pora crassa Ulr., may be compared through Stenopora? signata. 

 A clear line of relation passes from say, Rhombopora dicho- 

 toma. through R. incrassata, Anisotrrpa? elegantula Ulr., and 

 A. solida, to Stenopora ramosa. Again, if we pass from R. 

 siwulatrix, R. decipiens, R. tabulata and R. minor to R. ? 

 n*]>erula, but a short step is required to bring us to Batosto- 

 inella nitida and B. spinulosa. 



Despite the close relationship suggested by the above lines of 

 comparative inquiry, I have placed the two families in different 

 suborders. My reason for doing so is that, notwithstanding 

 the numerous points of agreement, there always remains one 

 peculiarity to disting-uish them. This is the presence of hemi- 

 septa in the RHABDOMESOXTID.E, and their absence in the BATO- 

 STOMELLID.E. These structures are known only among the CRYP- 

 TOSTOMATA, of which they constitute one of the most important 

 and characteristic features. That the primitive portion of the 

 zooecia of this family is tubular, is, I believe, largely accounted 

 for by the fact that the distance from the center of the branches 

 to their surface is too great to admit of short cells. The much 

 shorter zooecia of the new genus Coeloconus, which compare 

 favorably with those of the STICTOPORID.E, lend plausibility to 

 this view. Still I would not for a moment deny the importance, 

 from a morphological point of view, of the relationship above 

 shown. 



(10) STREBLOTRYPID.E: In this family the zoarium may be 

 ramose, bifoliate, or unilaininar, the primitive portion of the 

 zocecia tubular in the first, and sub-tubular in the other modes 

 of growth. Hemisepta may be present or wanting. The aper- 

 ture which is usually circular, or elliptical is in other forms 

 decidedly truncated at the posterior margin. The front of the 

 cell back of the aperture, is simply depressed or exhibits from 

 two to twelve or more small pits. When the latter are numer- 

 ous they are generally arranged in two longitudinal series. 



