162 
Rev. T. Hincks on the 
This genus is instituted for two or three species which 
seem to lie outside the preceding group, though nearly related 
to it. P. iabrosa : with its triplet of denticles, its elevated 
peristome, and its porous surface, exhibits much affinity with 
such forms as S. Lcindsborovii and S. crystallina. P. eximia 
agrees with it in most points ; but the pores are only present 
round the margin. In P. collaris both pores and denticles 
have disappeared. The chief distinction between this genus 
and the last lies in the character of the secondary orifice, 
which in Smittia contracts in front into a deep channelled 
sinus, whilst in Phylactella it is rounded in front and entire. 
The primary orifice in the present group is almost semicircu¬ 
lar ; and there is a total absence of avicularia. 
Escharoides or Eschara, Smitt. 
Under one of these names two species may be associated, 
which, I believe, exhibit essentially the same structure of cell, 
though the zoarium is in one case compressed and branched, in 
the other cylindrical, and, as far as we know, simple—dif¬ 
ferences which are not of any special importance. 
Zocecia with the primary orifice suborbicular; peristome much 
elevated, and forming a secondary orifice, arched above and 
with a sinus below, within which an avicularium is enclosed. 
Species : E. rosacea , Busk. 
E. quincuncialis , Norman. 
Mucronella, Hincks. 
This genus is equivalent to the Discopora of Smitt, but not of 
Fleming, who originated the name for species belonging to a 
totally different section of the Polyzoa (the Cyclostomata), 
with which it is still connected in the slightly modified form 
Discoporella. It includes a considerable number of British 
species, which constitute one of the best-defined groups in 
this section. 
Species : M. Peachii , Johnston. 
M. ventricosa , Hassall. 
M. variolosa , Johnston. 
M. laqueata, Norman. 
M. abyssicola , id. 
?ilf. microstoma , id. 
M. coccinea , Johnston. 
?J/. pavonella, Alder. 
Palmicellaria, Alder. 
From a careful study of the structure and development of the 
