FL0R1DAN BRYOZOA. \) 



beyond the colonial organs possessed by the typical Membranipora unicornis, it deve- 

 lopes avicularia, whose nearest correspondence we lind on the true Reteporce; although 

 sometimes, even in the European seas, on the common Membraniporidan growth ') the 

 same colonial organs can be developed without any remarkable alteration of the 

 other parts. 



The two specimens of Membr. sigillata, which were sent me for examination, 

 give a very complete knowledge of the variability of the species. What I take to be 

 the most typical form, is that most resembling the common Membr. unicornis. The 

 zooecia are placed in alternating rows, two or sometimes three in the breadth of a 

 branch. They show the common form of the Membr. unicornis, with two pairs of spines 2 ), 

 where the ooecia are wanting, and with one pair only in front of an ooecion. The 

 inner lamina, in the areas, is well developed, as it was in the preceding form of this 

 group. Where the ooecia are developed, with the charaeteristical transverse rib, they 

 are crowned by the common avicularia, which thus seern to be sessile upon them; 

 but in wanting of the ooecia, these avicularia are raisecl, as on the Membr. minax. 

 On the sides of the branches, as well as on their back, other avicularia are developed 

 of a greater size and more sessile, navicular like those of Membr. discreta. The tip of 

 their beak is curved and the margin of their opening (area) denticulated. At the 

 back of the branches (lig. 65), the limits of the zooecia are very apparent. The calci- 

 fication in their wall on this side presents a rounded or elongated thinness in their 

 middle, the best reminiscence, I think, from the encrusting state of the species, in what 

 condition the whole wall of the back side of the zooecia is less calcified. The scattered 

 avicularia on the back of the stena have the same form as those on its sides, but 

 usually they have the distal end (the tip) more raisecl, thus taking a more oblique 

 position. 



The root of the stem is all too little developed for giving any good idea of 

 the encrusting state, but in the British Museum I have seen a specimen, taken from 

 37 fthms. at Lat. 41° 30' n., Long. 141° east, that, 1 think, must be referred to the 

 same species, though it does not show any raised portion. 



The original specimen (figs. 67 and 68), described by Pourtales, at first sight, 

 perhaps, would be separated as a distinct variety from the preceding one; for in all 

 its parts it presents a more elongated form, thus, for instance, showing the median 

 avicularia (fig. 67) more raised and pedunculated, what is rendered more conspicuous 

 by its wanting of the ooecia. But, in accordance with many other bryozoa, these dif- 

 ferences very easily will be accounted for as depending on a more advanced colonial 

 evolution. 



Now, if the Reteporidan growth does not give us any reason for inaking a new 

 genus, consequently the same must be said about the Cupularian growth. Thus, as 

 its zooecial form brings it very near to the preceding ones, I name 



') Oa the Membranipora discreta, see Öfvers. Vet. Akad. Förh. 1867, pag. 396 etc. 



2 ) Very often the oue of the inner spines is wanting, as it usually occurs even on the Celiularina. 



2 



K Vet. Åkad. Handl. 13. 11. N:o 4. 



