1875. ON ALCYONCELLUM SPECIOSUM- ETC. 607 
lacerati ; in valvula sinistra dens lateralis inter duos valvule 
dextre insertus. 
Long. 1 poll., lat. 1) poll. 
fab. Birmah, vel Pegu. 
Mus. Hanley. 
The beaks are eroded in our only specimen of a shell (Conch. 
Indica, pl. 155. f. 3), which reminds us somewhat in structure of 
the Unio tavoyensis of Gould. When held before a light the valves 
appear of a yellowish green, richly embossed with zigzag ridges of a 
darker or bluer verdure. ‘The hinge is nearly the same as in U. favi- 
dens of Benson, the central teeth being short and very complicated. 
5. Further Observations on Alcyoncellum speciosum, Quoy et 
Gaimard, and Hyalonema mirabile, Gray. By J. 8. 
Bowersank, LL.D., F.R.S., F.Z.S., &e. 
[Received September 24, 1875.] 
On Wednesday the 8th September, 1875, I received a jar of spe- 
cimens from Commodore Parish, of Hong-Kong, which he stated he 
obtained from tlre ‘ Challenger’ when there. The specimens were 
preserved in spirit in the condition in which they were taken from 
the sea. They consisted of two specimens of Alcyoncellum speciosum 
with their dermal membrane and sarcodous substance in a fine state 
of preservation, one fine specimen of Hyalonema mirabile with 
the basal sponge in fine condition and with its dermal membrane in 
perfect preservation, and a fine head of a recent pentacrinite with 
about three inches of its stem with side arms in a good state of pre- 
servation. ‘These specimens, especially those of Alcyoncellum spe- 
eiosum and Hyalonema mirabile, are exceedingly interesting, as their 
perfect state of preservation enables us to complete our knowledge of 
their anatomical peculiarities to a much greater extent than those, in 
a more or less imperfect condition, with which we have hitherto been 
acquainted. _On mounting in Canada balsam small portions of the 
two specimens of Aleyoncellum speciosum, I found in a fragment 
from near the distal end of one of them the beautiful dermal expan- 
sile system of reticulated structure, composed of slender rectangulate 
sexradiate spicula, the distal ray of each terminated by a spinulo- 
quadrifurcate sexradiate stellate spiculum, which is so beautifully 
exhibited in the highly interesting skeleton of the specimen from a 
sponge of the same species presented to me by my friend Dr, Millar, 
and described by me in Part 1V. of my “ Monograph of the Siliceo- 
fibrous Sponges,” in the Society’s ‘Proceedings’ for 1875. ‘The 
complete envelopment of these beautiful tissues by the dermal sar- 
code of the specimens in a natural state renders the identification 
of these delicate defensive organs by no means an easy task; and in 
truth, without the indications of their forms and proportions af- 
forded by Dr. Millar’s specimens, we could scarcely have hoped to 
detect them 2” situ amidst the dense amber-coloured sareode in 
Proc. Zoou. Soc.—1875, No. XXXIX. 39 
