234 
some respects an intermediate stage between the species of Halo¬ 
mitra with smooth spines and those of the genus Ddderleinia. 
Besides the species belonging io \\\s gQuus Doderleinia Gardi¬ 
ner (1909) recognizes as true species of Halomitra only four of 
Studer’s (1901) species, viz. H. pilens (Dana), H. tiara (Agassiz), 
H. concentrica Studer, and H. philippine nsis Studer. The other spe¬ 
cies which were placed by Studer in this genus are in reality 
representatives of other genera. As for H. fangites Studer there is 
much evidence that it is an abnormally developed Fungia fangites 
(cf. above). 
Madrepora pilens L., which was based on Rumphius’ Mitra 
polonica is a representative of the genus Halomitra as I have 
already pointed out in the previous pages under Herpolitha Umax. 
Halomitra pilens Dana and H. pilens M.-E. & H. probably are based 
on somewhat dilferent forms and perhaps both of these again differ 
from Rumphius’ species. 
As already has been stated by Gardiner (1909) the four 
species pilens, tiara, concentrica and philippinensis, as these have 
been defined by Studer (1901), seem to be closely related. Many 
of their specific characteristics, however, are subject to strong 
individual variation, caused by external influences. With the except- 
ion of H. pilens Studer they cannot be distinguished as dilferent 
species and I have therefore united the three other forms under 
the name H. philippinensis. 
Halomitra pilens Studer is in all probability the same form as 
H. pilens Dana (= H. clypens Verrill). I have examined a speci- 
men from Fiji, collected by the U. S. Exploring Exp., in the U. S. 
National Museum, which was labelled Halomitra clypens. Probably 
this specimen is the type of the species. The corallum is rather 
thick, the costal spines are strongly developed (larger than in H. 
philippinensis) and almost quite smooth. The septal dentations are 
usually blunt, the septa are as a rule thicker than in H. philip¬ 
pinensis. On account of these differences H. pilens Dana has to 
remain separated from H. philippinensis Studer. 
As for Halomitra tiara Agassiz (cf. also Studer, 1901) the 
specimen in the Museum of Comparative Zoology in Cambridge 
(Mass) differs from the specimens in my material which I refer 
