368 Mr. Toulmin Smith on the Classification 
of the tube is the same in each. But masses of the two cannot 
be confounded, and the specific distinctions, as noticed in treating 
of B. tubulatus, are very important. It should be further noticed 
that,* in the present species, there is not that variety in the size 
of the tubes which, as seen in fig. 7. PI. XV., is found in B. tu- 
hulatus. 
A certain degree of regularity is generally found, on careful 
observation, in the arrangement of the anastomosing tubes ; that 
arrangement bearing often a near resemblance to regular square 
lattice-work. This arrangement extends both in the horizontal 
and vertical plane, as endeavoured to be represented in fig. 3, 
PI. XVI. Specimens sometimes attained a large size. 
Both this species and the last are very beautiful fossils when 
they can be obtained in any degree of perfectness. This how- 
ever is extremely difficult, owing to the small branching arms of 
which each is made up. The inquirer may, unless great care is 
bestowed, and very cautious dissection made, easily mistake for 
them some of the markings often found on accidental fracture of 
chalk and flint, and on the outsides of flints, and which are really 
caused by B. foliaceus or other of the sinuous species. Oblique 
fractures take very indeterminate forms. 
This species is found in the Chalk Marl and Upper Greensand. 
I have never seen a specimen from any higher beds. 
6. Brachiolites lahrosus. PI. XVI. fig. 4. 
Membrane having a slight and irregular primary fold : brachial 
fold variously winding and irregularly anastomosing, thus 
forming irregular but wide sinuous cavities opening into each 
other, with slightly projecting wide and irregular openings 
having entire and rounded margins : mass compact, broad and 
wide ; rising to a moderate height, and subglobose in form. 
The description will at once enable the inquirer to distinguish 
this very marked form from every other. The character of the 
primary fold resembles that of Ventriculites impressus. It is not 
nearly so close as in B. tubulatus, but much closer than is usual in 
B. protensus. The mouths of the cavities rarely open, as in B, 
fenestratus, by a regular cylindrical tube, but are very often elon- 
gated or irregular, and more or less constricted near the middle. 
The margin, however, is in every case entire, and generally 
spreads outwards, thick and lip-like, whence the name. The 
figure exhibits these peculiarities, but the size of the plate did 
not allow space for the representation of an entire specimen. 
This species is found in the Chalk Marl and in the Upper 
Greensand. I have seen it from no higher beds. 
