7 
be found in the number of tentacles of the gastrozooid, giving 12 as the number in AZopora 
and 8 in Stydaster; but the number of tentacles on the gastrozooids is much too variable for 
diagnostic purposes. In S. graczlis') 12 tentacles have been found and we have found in 5S. 
filogranus 4,5, 6 or 7 tentacles. 
As regards the characters mentioned by Mose.ry in these words ‘a strong tendency 
towards the development of the cyclosystems on the lateral margins of the branches only. 
Cyclosystems arising from one another by alternate gemmation’’, we may say that the alternate 
gemmation is only pronounced in those forms arranged in the groups A. and ZY. in which 
g 
the cyclosystems are confined to the lateral sides of the branches, or to one surface only of 
the flabellum. In the other groups the alternate gemmation is not nearly so conspicuous, even 
if, in some cases, it may be rightly said to occur at all. 
However for the present we think it is advisable to keep the species attributed to 
Allopora distinct, fully recognising the close relationship they have with this large and very 
variable genus. 
This is the most abundant and widely spread genus of the family. No less than 29 species 
have been described. They may be arranged according to a suggestion of StupER”) as follows: 
A. Cyclosystems on lateral sides of the branches only. 
S. flabelliformis Milne Edwards and Haime. S. bellus Dana. 
S. gracilis Milne Edwards and Haime. S. ¢enuts Verrill. 
S. amphiheloides Saville Kent. S. extmius Duchassaing and Michelotti.  : 
\S. punctatus Pourtales. S. daevis Studer. 
‘S. filogranus Pourtales. S. verrucosus Studer. 
S. asper Saville Kent. S. bclobatus sp. n. 
S. densicaulis Moseley. S. multiplex sp. n. 
S. txfundibulifera Lamarck. 
B. Cyclosystems on lateral sides of branches and a few on the surfaces. 
S. voseus Milne Edwards and Haime. S. evubescens Pourtales. 
S. sanguineus Milne Edwards and Haime. S. elegans Verrill. 
S 
. pulcher Dall. 
\.S. gemmascens Milne Edwards and Haime. 
C. Cyclosystems evenly distributed over the surfaces of the branches. 
S. granulosus Milne Edwards and Haime. S. stellulatus Stewart. 
D. Cyclosystems on the anterior surface of the branches only. 
S. complanatus Pourtales. S: feleatus Sp. ti: 
S. obliguus Studer. S. minimus sp. n. 
S. virgints Moseley. S. umbonatus sp. n. 
1) 8. J. Hickson. Proc. Roy. Dublin Soc. VII, 5. 
2) TH. StupER. Monatsber. der K. Akad. Berlin 1877. 
