644 
Proceedings of Royal Society of Edinburgh. [sess. 
one another a short distance from centre whither they are con- 
tinued as a simple line ; the compartments reaching from -| to £ 
of radius inwards, their inner ends transversely truncate or hut 
slightly convex, areolate ; the intervals attenuating gradually 
outwards, their outer ends slightly swollen and knob-like. 
Greville has pointed out that the geniculate flexure of the rays 
found also in Aster omphalus imbricatus , Aster om. Darwinii , 
Aster om. elegans , Aster om. Brookei , and in a less degree in Aster om. 
sliadboltianus , goes to establish the validity of the union of 
Aster omphalus and Asterolamyra into a single genus, but this 
ignores the apparently more constant characters in the latter con- 
nected with the subobsolete interval between two of the compart- 
ments. 
Habitat. — Monterey stone ( Walker- Arnott). 
A. Grevillei. Grev., Trans . Micr. Soc. Lond ., 1860, p. 113, 
pi. iv. fig. 21. — Diam. *075 to - 085 mm. Central areolate area 
absent, sometimes represented by two plano-convex areolae. Mark- 
ings : rays straight, or gently arcuate, diverging from an angular 
arched central line rarely from a central point ; the compartments 
reaching about J of radius inwards, their inner ends curved or 
flattened on opposite sides of rays convex towards the centre, their 
margin formed by a narrow subhyaline band, elsewhere minute sub- 
punctiform granules, least evident towards the border, sometimes 
unresolved; the intervals of uniform breadth; their outer ends trans- 
versely truncate, sometimes terminating a considerable distance from 
the border. Border narrow, indistinct. — Aster omphalus Grevillei , 
Wallich, Trans. Micr. Soc. Lond., 1860, p. 47, pi. ii. fig. 15. 
The radii vary in number from 7 to 17, and exhibit considerable 
variation in their mode of origin, an adjacent pair frequently 
uniting and being connected by a common short central stalk with 
the central portion. 
Habitat. — Moron deposit (Greville ! Hardman !) ; Indian Ocean 
2200 fathoms, Captain Pullen (Wallich); Eappahannock deposit, 
U.S. (E. W. Dallas) ; Monterey stone (Walker- Arnott). 
A. princeps * nov. A. Grevillei , var. eximia. Cstr., Diat. Chall. 
* The name eximia “cannot be adopted, as it has been preoccupied by 
Greville {Trans. Micr. Soc. Lond., 1865, p. 99) for a distinct form (see infra). 
