Among the numerous organic relics embedded in black limestone at
Trenton Falls, in the State of New York, there is often found the
fragment of a trilobite which cannot properly be referred to any of the
genera already mentioned. Dr. J. Bigsby, in his Sketch of the Geology
of the Island of Montreal, has figured and described a fossil which
occurs at that place, which approaches in its specific characters to
the fragments found at Trenton--but he does not suggest for his relic
any name. Professor Brongniart has also represented, plate 4, figs.
5 and 7 A. B. C., the fragments of trilobites from Russia and from
Llandillo, in Wales, which seem to differ but little from those above
noticed, these are also without names. Under such circumstances, we
have thought it expedient to group these relics under the generic term
of Cryptolithus, a name analogous to Calymene, Asaphus, Ogygia, and
Agnostus, and which may with propriety be applied to the animal, should
it ever be discovered entire.[42]
[Footnote 42: Since the above was written, and the C. Tessellatus
published, I have received a fine specimen of this trilobite from
Professor Eaton, in an almost perfect state, so that the entire animal
can now be described.]
_Body_, contractile.
_Buckler_, lunate, convex, outer edge surrounded by a semicircular,
reticulated, or tessellated border.
_Front_ or middle lobe of the buckler very protuberant.
_Oculiferous protuberances_, none.
_Abdomen_, much compressed, trilobate.
Cryptolithus Tessellatus. _Green._ Cast No. 28, and Fig. 4.
Clypeo rotundato, fronte valde convexo, capite antice semicirculari
margine tessellato ornato.
Outline of the buckler hemispherical, the edge surrounded by a
semicircular border of tessellated or rounded punctures, in three
concentric rows in front--on each side near the posterior angle of the
buckler, these rows of punctures are more numerous; the front is highly
convex; is rounded before, and gradually tapers towards the abdomen.
The cheeks form spherical triangles, and are entirely destitute of
oculiferous tubercles or any other markings; their posterior angles
project beyond the sides of the abdomen. Abdomen and tail very much
compressed, and composed of about ten articulations; costal arches of
the lateral lobes grooved; tail attenuated. Whole length half an inch.
The Cryptolithus Tessellatus, resembles a good deal the Entomostracites
Granulatus of Wahlenberg, and which Dr. D aim an calls Asaphus
Granulatus. The figure of this animal given by Brongniart, table 3,
fig. 7, appears to be quite imperfect, and is very unlike, except
in the buckler, the representation of Wahlenberg's fossil, given by
Dalman, table 2, fig. 6. Though the angles of the buckler in the
Asaphus Granulatus are much more elongated than those of the C.
Tessellatus, it may perhaps be another species of the same genus.[43]
[Footnote 43: The following, is Dr. Dalman's description of the Asaphus
Granulatus:--
A. trunco sexarticulato pygidioque lævibus, capite antice
semicirculari margine granuloso, angulis posticis extensis corpore
longioribus.
Animalculum singulare, inversum si inspicitur, lyram forma fere
similans. Caput antice semicirculare, margine distincto, serie
submoniliformi e granulis approximatis ornato, discus capitis
lævis, sed ambitus intra marginem punctis elevatis obsitus. Hic
ambitus, una cum margine, truncum quoque amplecti videtur, ad
pygidii basin usque, ubi in cornua lævia, trunco multo longiora,
abit. Glabella antice fere clavæformis, ad basin utrinque emittens
lobi rudimentum. Truncus brevis lævis segmentis constans tantummodo
sex, rhachide angusta. Pygidium breve, rotundatum, læve; adeo
parvum ut ne quidem capitis disco respondeat.
Obs.--Oculos atque suturam facialem ex autopsia describere licet.
Vide Om. Palæaderna eller de sa kallade Trilobiterna af. J. W. Dalman,
pages 50-4. ]
The animal described and figured by Dr. J. Bigsby, to which we have
already referred, seems rather different from our species. His
specimens were found at Montmorenci, near Quebec, (Canada) more than
an inch and a half in diameter. The following are his remarks on this
trilobite.[44] "The front of the buckler is remarkably convex, and has
on each side near the base, three very small transverse lines, scarcely
to be called depressions, corresponding to the sulci so strongly marked
in the genus Calymene. There is frequently, but not universally, a
very minute pisiform process on the centre of the front. The whole
upper edge of the buckler is always surrounded by a very ornamental
semicircular border, sometimes semi-elliptical, of punctures placed in
the meshes of a net-work in high relief and arranged close together,
in rays, passing perpendicularly from the buckler and forming at the
same time when observed transversely, curved lines parallel to its
upper rim or edge, excepting at the sides, where they diverge, leaving
a space occupied by other lines of dottings, parallel to the former,
but speedily terminating on the cheeks of the buckler. The lines which
are complete from side so side, are four in number. The imperfect
additional ones, vary from two to four; the smallest and inner,
consisting only of two or three punctures. A plain edging includes the
semicircle of punctures. In the beds of these casts, the places of
the punctures are shown by small conical elevations, and those of the
ridges of the net-work, by corresponding depressions."
[Footnote 44: See Geology of the Island of Montreal, in Lyceum of Nat.
History, N. Y. p. 214.]
Should this prove to be a distinct species, we propose to call it
_Cryptolithus Bigsbii_.
The _Nuttainia Concentrica_ of Professor Eaton seems also very nearly
allied to this species; he describes it as having "four or five
concentric arcs of punctures in front of the buckler, separated by
alternating arcs of fine elevated ridges." The genus Nuttainia, to
which he refers this species, cannot include it, and the N. Sparsa; for
these two relics have scarcely a single essential character in common;
we have, therefore, confined the genus Nuttainia, to the species which
he calls _Sparsa_.
The Cryptolithus Tessellatus is very common at Trenton falls. In the
transition limestone at Glenn's falls, in the state of New York, during
a very short visit to this place, Dr. R. Harlan procured a large number
of this fossil, but only the buckler, the projecting front of which
exhibited a pisiform protuberance above the level of the strata. Mr.
Eaton says that the N. Concentrica "occurs in the wacke variety of
transition of argillite, on the Champlain canal," between the town of
Waterford and the Mohawk river. The specimen in my cabinet, from which
our cast was made, is from that place.
The Cryptolithus Tessellatus occurs also in the limestone which,
according to Dr. Bigsby, overlays the sandstone in the island of
Montreal. At most of its localities, it is associated with the
Isotelus, the Calymene, and with several species of Asaphus. The
Cryptolithus, which is entirely destitute of eyes, being thus found
with the oculiferous species, is an interesting fact, and controverts
the opinion of Professor Wahlenberg, that the trilobites, which are
without eyes belong to a geological epoch more ancient than those which
are furnished with oculiform tubercles. That organic remains furnish us
with the most satisfactory evidence of the identity or dissimilarity
of certain formations, is a disputed point with some geologists[45] It
cannot reasonably be doubted, that new and isolated facts have been
made the basis of a too hasty generalization. On this subject Count
Rasoumowsky makes the following remarks:--"Les divers gisemens des
Trilobites ne me semblent pas non plus pouvoir être déterminés avec
quelque précision. M. Brongniart parait admettre que les trilobites
aveugles ne se trouvent que dans de tres anciennes formations dans
des schistes et des calcaires de transitions; mais nous avons donné
la description d'un trilobite [without eyes] des bords de la Yaousa
prés de Moscow, qui n'appartient certainement pas aux formations de
transition, ce qui me donné lieu de croire que de nouvelles recherches
et de nouvelles observations, prouveront qu'il n'est pas strictement
vrai qu'en France, en Angleterre, en Russie, _il n'existe point de
trilobites entiérement privés d'yeux_, comme le dit le savant auteur
que je viens de citer." See Annales des Sciences Naturelles, Vol. 8.
page 195.
[Footnote 45: See Eclectic Review, for July, 1832.]