8 F. A. SMITT, 



Bahia l ). Now, I think, only a direct comparison of typical speciinens can decide, whe- 

 ther the four above-named species are good systematical ones or ought to be united. 

 But both for the locality and for the agreement with the figures, I venture to name 

 the Floridan form 



Idmonea Milneana (Pl. III, tigs. 14—17). 



In the size of the zooecia as well as in the general appearance of the bryozcm- 

 rium, it comes nearest to the Idm. serpens, but the branches of the dichotomously di- 

 vided stem are generally more straight and slowly widening upwards against the new 

 diehotomisation. The typical number of the zooecia, (see tigs. 14 and 16), in the trans- 

 verse rows, seems to be 3, but in the lower parts of the branches they often occur 

 with only 2 and sometimes a single one. This induces me without hesitation to refer 

 to this same species a little part of a stem in its beginning (see fig. 17) that I tind 

 growing on another bryozoon, brought up from the same locality and in the same 

 cast as the typical and more high-grown speciinens. Viz. the size of the zooecia, their 

 punctation and arrangement. as well as the hyaline ectocyst, so closely agree with the 

 lower part of one of the other speciinens, that there can be no doubt, I think, of their 

 belonging to each other. I, therefore, consider this little fragment as showing the same 

 laAv of development, we generally find in these Cyclostomata, that they arise from sim- 

 pler forms with the zooecia single or aggregated 2 and 2. Bnt the most striking appear- 

 ance in this, a fragment of the lowest part of a stem, that gives it a greater interest 

 of systematic value, is the mode in which it is tixed upon the foreign bryozoon. The 

 first zooecia, at the origin of the stem, are unfortunately löst, but so rauch is left, that 

 we can see, how it first crept an Alecto, very similar to the A. gränulata. From this 

 stage it is raised; but instead of forming a crust-like basal expansion, such as usually 

 occurs in this group (»empatés,» DOrb.), at four points it sends down radiciforip. pillars, 

 composed of prickled calcareons tubes. This aberrance from the coinmon mode of fix- 

 ing the stem may here be quoted, like the Escharella palmata 2 ) and. others among 

 the Chilostomata, as an example of the difficulties in grouping the families according to 

 that principle. 



On the back side of the stem we find the same punctation and striation as on 

 the other typical Idmonece : fignre 15 shows it reticulated by strise, and these meshes 

 we know to be the proximal ends of the zooecia. But in the higher calcinations, 

 these markings are more obscured, at the same time that the transverse striation usu- 

 ally becomes coarser; and this, I think, will make it very probable that the typical 

 striation could escape the notice of D^rbioxy. 



It is often the case, that the species are altered in a certain mode by going 

 lower down to the greater depths, where they usually become elongated and retain a 

 simpler form. The above-named Idmonea flexuosa showed such a relation to the Idm. 

 atlantica ; and now Pourtales has brought up from 450 fathoms, off Cojina, Cuba, a 



\) In the Quart. Journ. Geol. Soc, vol. XVI, pag. 261, Busk mentions the Idmonea Milneana as found by 



Rev. Woods in a Crag-formation near Moiait Gambier, South Australia. 

 2 ) See: Krit. Fört. Shand. Bryoz., Öfvers. Vet.-Akad. Handl. 1867, Bih., pag. 79 etc. 



