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]
[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.