274 DR. J. S. BOWERBANK ON [Apr. 6, 
I am indebted to my late friend Mr. Henry Deane for two speci- 
mens of this interesting species ; neither of them exceeds 8 lines in 
height and 5 in greatest diameter. From their form and other 
external characters they might readily have been mistaken for 
specimens of Farrea gassioti; but a microscopical examination 
readily separates them from that species. As was the case with F. 
gassioti, the characters derivable from the dermis, oscula, and pores 
were not available; so that the discrimination of the species was in a 
great measure dependent on the structural peculiarities of the ske- 
leton ; and the resemblance of the two species in size, form, and mode 
of arrangement of the spicula is very close; but they differ very 
strikingly in the characters afforded by the central canals of the ske- 
leton-structure. In those of P. gassioti, when examined beneath the 
microscope in Canada balsam with a power of 108 linear, they are 
strikingly large and distinct, while in F. pocillum, although the 
fibres of the two species are as nearly as possible of the same size, 
they are remarkably slender, and in some cases nearly obsolete ; and 
this was the case in portions taken from both of the specimens in my 
possession. These distinctive characters are quite sufficient to 
separate the two species; but there are fortunately others that aid 
materially in their discrimination. Thus in F. pocil/um there are 
numerous internal defensive organs of a rectangular sexradiate 
form, based on the sides of the skeleton, and projected into the areas 
of the rete. These organs are comparatively large and strong; and 
are abundantly furnished with large conical spines. Sometimes the 
primary central portion of these organs is destitute of the four 
lateral radii ; and occasionally the lateral radii are doubled in number, 
a second set of them being projected beyond the first ones. In 
addition to these internal defensive organs there are numerous unat- 
tached rectangular sexradiate spicula, occasionally grouped together 
in considerable numbers on the areas of the skeleton-rete. These 
spicula are very distinct from those organs of the same form which 
are based upon the skeleton-fibre ; they are very much smaller, and 
their radii are slender and usually spineless.. All are alike acutely 
terminated, and have evidently never been based upon the skeleton- 
fibres, as the organs first described always are. The presence of 
these organs in the one species and their apparent complete absence 
in the other strongly confirms the propriety of their separation, not- 
withstanding the close resemblance they bear to each other in 
external form. 
The specimens were dredged July 22, 1872, in lat. 14° 8'N., 
long. 77° 38' W., 800 to 1000 fathoms, by Capt. Hunter, R.N. 
Deane, Bowerbank. 
Skeleton siliceo-fibrous. Fibres canaliculated ; canals continuous. 
Rete symmetrical ; areas rotulate, confluent. 
This genus is intermediate between Iphiteon of Valenciennes and 
Farrea. The skeleton has the confluent rotulate structure of the 
former, but differs from it in having the fibres distinctly canalicu- 
lated. It agrees with the latter genus in the canaliculation of the 
