114 
Greville^ on Asterolmnpra. 
Indian soundings^ having a very irregular and curious arrange- 
ment of the umbilical lines. 
5. Asterolampra Brebissoniana, n. sp. Grev.^ — Areolated 
segments square at the base ; umbilical lines with an angular 
bend in the middle. Diameter -0030 (PI. Ill, fig. 9.) 
Hab. — Monterey stone, Professor Walker- Arnott. 
This may be regarded as one of Professor Walker- Arnott^s 
most interesting discoveries, as it shows that the very remark- 
able angular bend in the umbilical lines, already known to 
exist in some species of Aster omphalus and Spatangidiurrij 
is not excluded from the present section ; and therefore 
strengthens, in however small a degree, the argument in 
favour of the union of the whole group into one genus. I 
have much pleasure in dedicating so well-marked a species to 
M. Alphonse de Brebisson, whose name is so eminently asso- 
ciated with these wonderful structures. 
Section II. — Rays unequal (one much narrower than the 
rest) . Umbilical lines radiating from the central point ; two 
of them approximated. — Asteromphalus. 
6. Asterolampra Hookerii. — Areolated segments curved at 
the base ; umbilical lines straight, the two approximated ones 
(median lines) parallel. 
Asteromphalus Hookerii, Elir., Berl. Monatsb., 1 844, p. 200, pi. (June), 
fig. 3 ; Kiitz., Sp. Alg., p. 129 ; Pritcli., Animalc., p. 321 ; Mic. 
Diet., p. 71, pi. xix., fig. 2 ; Elir., Miia-ogeol., pi. 35, A. xxi., fig. 2 
(6 rays). 
Asteromphalus Buchii, Ehr., Berl. Monatsb., 1844, p. 200, fig. 4 ; 
Kiitz., 1. c., p. 130 ; Pritch., 1. c., p. 321 ; Mic. Diet., p. 71 (7 
rays). 
Asteromphalus Humboldtii, Ehr., Berl. Monatsb., 1844, p. 200, fig. 6 ; 
Kiiiz., 1. c., p. 130; Pritch., 1. c, p. 321, pi. xiv., fig. 34 ; Mic. 
Diet., p. 71 ; Ehr., Mikrogeol., pi. xxxv., A. xxi., fig. 3 (8 rays). 
Asteromphalus Cuvierii, Ehr., Berl. Monatsb., 1844, p. 200, fig. 7 ; 
Kiitz., 1. c, p. 130 ; Pritch., 1. c, p. 321 ; Mic. Diet., p. 71 ; Ehr. 
Mikrogeol., pi. 35, A. xxi., fig. 1 (9 rays), 
Hab. — The Antartic Ocean, Dr. J. D. Hooker. 
As the celebrated Ehrenberg regarded a simple diflFerence 
in the number of rays as amounting to specific distinction, 
he has added a multitude of names to our list of Diatomaceae 
which cannot now be permitted to retain their position. 
Such is pre-eminently the case in the genera Actinocyclus and 
Actmoptychus, which will probably be found ultimately to 
contain comparatively few true species. In Asteromphalus the 
same system was carried out. The four species now brought 
together are only distinguished by each individual having 
