324 SIDNKY F. HAKMER. 



circular and uncalcified, while the greater part of the zooecimn 

 is constituted by the cylindrical lateral walls, 



I do not know of any Flustrine form in which the ancestrula 

 is other than Flustrine in respect of its frontal wall. In 

 Membraniporella nitida the ancestrula is Tata-like^ and 

 shows clearly that the four oral spines are of the same nature 

 as the remaining ten marginal spines figured by Hincks. 

 This species is particularly interesting in the fact that some 

 of the older members of the colony produced by budding 

 may retain the Membranipora-like condition (Hincks, 

 1880, pi. xxvii, fig. 7), and possess a series of irregular 

 marginal spines which do not unite. The remaining zooecia 

 have their frontal spines arranged with the regularity 

 characteristic of the Cribrilinidse in general. 



The consideration of the Cheilostomata in which the 

 ancestrula is not Tata-like is almost as instructive as that of 

 the first set of cases. 



In Hippothoa hyalina, Jullien (1888, 4, p. 29) states 

 that the characters of the ancestrula are variable. In Euro- 

 pean specimens the frontal wall is fully calcified. The same 

 condition was found in specimens from Tierra del Fnego, 

 although in most of the colonies from this locality the 

 ancestrula was a circular Tata-like zooecium, witli a large 

 meinbranous aperture bordered by six inwardly curving 

 marginal spines (Jullien, pi. iv, figs. 1 — 3), while in a third 

 case (ibid., fig. 4) the ancestrula is at first Tata-like, but the 

 membranous aperture subsequently calcifies, so that the orifice 

 normal for the species is contained in a calcified oral region 

 surrounded by the circlet of marginal spines. This leads to 

 the form described by Jullien as Diazeuxia reticulata 

 (ibid., fig. 5), in which the orifice of the ancestrula is 

 completely Schizoporelliform. 



Neviani (1898, p. 165) describes three viu-ieties of the ances- 

 trulaof Microporella malusii. The fii'st of tlieseisau ordi- 

 nary Tata form with ten marginal spines. Tiie second more 

 neiirly resembles the normal zocecium of this species, but 

 agrees with one of the ancestrula? described by Jullien (see 



