EAELY TEHTIAEY CTTETLOSTOME BRYOZOA. 59 



Genus TESSARADOMA Norman, 1868. 



1SG8. Tcssamdoiiia Norman, Report 3Sth Meeting, British Association for 

 the Advancement of Science, p. 309. 



The apertura is provided with cardelles. The frontal is surrounded 

 by areolae and covered by a pleurocyst. The spiramen opens at the 

 level of the operculum. The operculum in opening closes the spira- 

 men. 



Genotype. — Tes.'<aradoma {Pustnlopora) gramle Sars, 1850. 



Range. — Jacksonian-Eecent. 



In spite of Jullien's observations, the exact nature of the spiramen 



is still doubtful; its place and its function are not yet elucidated. 



Several species referred to this genus occur in the American Jack- 



sonian. 



TREMOTOICHOS, new genus. 



{Treiria., opening; toichos^ wall.) 



The frontal and the dorsal are tremocysts with sulci. The spira- 

 men opens interiorly at the level of the operculum; exteriorly it is 

 distant from the peristomice and almost never placed on the median 

 axis of the zocecia. 



Genotype. — TrenvotoicTws rectifurcatum^ new species. Jacksonian. 



This genus possesses all the characters of Semihasv)ellia ; the dif- 

 ference is little perceptible and consists solely in the place of the 

 spiramen. As the latter does not appear to exercise the same physio- 

 logical function (according to Jullien) as in SemihasweUia, we 

 believe it necessary to create a new genu.s. 



TREMOTOICHOS RECTIFURCATUM, new species. 



Plate 6, fig. 1. 



Description. — The zoarium is free, subcylindrical, branched almost 

 at a right angle. The dorsal is very thick ; deprived of avicularia and 

 formed of a tremocyst with tubules and with sulci. The zocecia are 

 indistinct ; the frontal is a tremocyst with sulci placed on an olocyst 

 with very small perforations. The peristome is salient, perpendicu- 

 lar to the zoarial plane, thick, and provided with a small proximal 

 avicularium ; the peristomice is orbicular. The spiramen is a pore of 

 the frontal placed on the right or left of the median axis and distant 

 from the peristomice. 



fA^;e— 0.10 mm. 



Measurements. — Peristomice . 7„._q ^q „-^^ 



Zocecia — Z5'=0.70 mm. 

 Variations. — The spiramen is not always apparent ; it is confused 

 with the tremopores. The peristome of the young zocecia is thin. 



