86 
0SCULIP0KID2E. 
In IS. gamhleij on the other hand, the main stems give off 
sub-branches which are usually opposite, and they are directed 
at a wide angle from the main stem ; and the main stem only 
dichotomizes after every four or five pairs of sub-branches. 
The typical branching of H. ramulosus is shown in d’Orbigny’s 
figures, pi. 797, figs. 5-7, and the shape of the sub-branches in 
his fig. 9 ; the branching of H. gamhleii?, shown on the same plate, 
figs. 11, 12, and 15. 
Fig. 28 . — Homososolen gambhi\ x 10. D. 7095. 
A second difference is that the reverse side in H. gamhlei is 
generally raised into a median keel or ridge, whereas that of 
S. ramulosus is flatter. This difference is well shown in d’Orbigny’s 
figures; his pi. 797, fig. 10, shows the flat-backed type of ramulosus^ 
and the fig. 14 on the same plate shows the triangular section and 
ridge of H. gamhlei. In old branches of H. gamhlei, however, the 
backs of the stems are flatter and covered by a calcareous layer 
marked by transverse wrinkles, while some narrow branches of 
ramulosus are sub-carinate. 
S. gamhlei is also a near ally of H. alternatus (d’Orb.), which 
differs by having shorter lateral branches that ai*e sharply reflexed. 
The pinnate zoarium of this species has some resemblance to that 
of S. disparilis (d’Orb.), from which, however, its structure is 
different, as in the greater length of the sub-branches and the 
absence of the saw-like lateral processes of that species. 
The specific separation of S. ramulosus and H. gamhlei is not 
free from doubt. One consideration that tells against the specific 
