ROEMER ON THE PENTREMITES.
9
ner lamiiine in two rows alternating with each other, and at length
towards the extremity larger laminar pieces in a single row. In the
specimen described the last are placed vertical to the plane of the
tentacular space .Fiihlerfeld), whilst the other part of the appendage
lies with its broad side on the plane of the space.
The length of the pinnulse is very considerable in relation to their
thickness : some of those originating at the lower extremity of the
jBeld can be followed even beyond the point of the interscapulary tra-
pezoidal piece.
The direction of all these appendages is very accurately towards
the vertex of the shell ; consequently in the middle of the tentacular
space they lie thickly compressed on each other, and this seems to
have caused that half-turning round of the tentacles, so that the
laminar portion of the upper extremity comes to be vertical to the
shell.
The number of the pinnulse in each row of a space (Feld) is about
fifty, which is also about the number of the holes in a row of the un-
covered, so-called, ambulacral space of a Pentremite of nearly the
same size.
In the annexed drawings, which my friend Dr. Ewald has had the
kindness to prepare, all the circumstances described are represented
with remarkable fidelity and care, and render any further description
unnecessary.
Fig. b.
Fig. c.
4P
/ ■ .
Fig. a. is a view of the specimen of the natural size.
Fig. b. a view of a tentacular space with the pinnulee, magnified
two times.
Fig. c. a single pinnula, magnified three times.
The most general result regarding the structure of the Pentremite
that may be deduced from the consideration of this specimen is : —