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Mr. H. J. Carter on new Species of Subspherous Sponges. 179 
larger ones (fig. 13, b b); while below the smaller spicule is more 
or less absent, and the radiating spicules become inclined to- 
wardsthe surface in the whorls, as above noticed (fig. 15). Canal- 
system distinct, but correspondingly condensed and small in 
its cavities, in accordance with the compact structure of the 
sponge generally ; presenting no evident arborescent form, but 
general diffusion between the nuclei (fig. 144). Spicules of 
two kinds only (fig. 16), viz. :—1, stout, straight, smooth, fusi- 
form, acerate or pointed at each end (a) ; and, 2, small, straight, 
smooth, slightly fusiform or acuate, pointed at one end only 
and the other rounded or obtuse (5). This spicule is, as above 
stated, chiefly confined to the upper surface, where, arranged ver- 
tically, with its sharp end outwards, among the points of the 
larger spicules, it contributes greatly to strengthen the surface 
and form a kind of crust. Size of sponge 2} inches by lys 
inch in horizontal and -4 inch in vertical diameter. 
Loc. et hab. Vera Cruz, Mexico. 
Obs. Described in the dried state. 
At first this sponge looks very much like a Tethya; but the 
absence of the furcate spicules, together-with its other diffe- 
rences in structure, soon shows that it cannot be classed with 
Tethya generically. Then the absence of the crust of globular 
erystalloids peculiar to the Geodide, with its numerous other 
differences from these, points out that it cannot be generically 
classed with either Geodia or Pachymatisma. And yet its 
dense rough character and cake-like free form evidently ally 
it to the subspherous sponges, so that it becomes necessary to 
a new genus for it in this family. Hence it has been 
called ^ Trachya,” from its asperous nature, which, although 
not a legitimate transformation of the word grammatically, 
nevertheless linguistically euphonizes sufficiently well with 
Tethya and Geodia to induce me to adopt it. 
It will have been observed that, although Trachya has not 
the exact elements of Tethya or Geodia for its crust, yet the 
addition of the small spicule arranged vertically in great num- 
bers among the projecting points of the large ones on the 
upper surface (fig. 13) supplies this apparent deficiency; while 
the number of nuclear centres in the internal structure not 
rr i causes the species to distinctly differ widely from Tethya 
and Geodia, but to assume that hardness and rigidity cha- 
racteristic of the subspherous sponges which nothing could 
impart better than this knotted structure. 
General Observations. 
I have also examined a third sponge belonging to the Mu- 
seum, which has grown upon the root of a ever and 
