291 
species' of Stegopoma, but at the same time he refers a species 
provided with the same form of operculum to the genus Cryptolaria. 
However, he thinks it likely 'that a separate genus should be 
instituted for this species and for Cryptolaria geniculata Allm., 
which possesses a similar form of operculum. As a' consequence 
of this standpoint Nutting mentions the genus Stegopoma as 
follows: "This genus ..... seems to me to be practically con- 
venient whether a natural one or not.” We meet in this genus 
with three different forms of growth. While St. (Crypt.) opercu- 
lata Nutt. and $t. (Crypt.) geniculata Allm. have a fascicled stem 
with an axial tube, St. plicatile and St, gilberti Nutt. possess a 
fascicled stem, in which all the tubes bear hydrothecae, and St. 
fastigiatum a creeping stem. The gonothecae are of two different 
forms which seem to be independent of the colonial form. In two 
Species with a creeping stem, described by Nutting, we find 
sessile gonothecae of a similar form as the hydrothecae, and the 
same is the case in $+. gilberti, while in St. plicatile and St. geni- 
culatum the gonothecae are elongate sacs without an operculum. 
Schneider!) thinks that the operculum of Campanulina (and 
Opercularella) must be. derived from the hydrothecal teeth of cer- 
tain Campanulariidae, which by attaining a sufficient length and 
thinness have been able to collapse and cover the hydranth after 
its retraction, but this is a more theoretical consideration, not 
sustained by any fact, and it may have been called forth by a 
comparion for inst. of the figures given by Hincks of Gonothyraea 
gracilis and Campanulina turrita, as the hydrothecal teeth in the 
former figure are very much like the segments of the operculum 
in the latter. But in G. gracilis as in all other dentate Cam- 
panulariidae the hydrothecal teeth are divided from each other by 
interstices which have once been filled by membranous parts, and 
these have been thrown off together with the hydrothecal roof. 
On the contrary in Cuspidella, Lafoéina and Oplorhiza as in Cam- 
panulina and Opercularella the operculum is formed by a continuous 
1) 54, p. 512. 
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