Part 4

Abdomen with about 8 articulations, without any dorsal longitudinal furrows.

Buckler sub-lunate, with large lateral eyes.

Tail expanded, not so large as the buckler, without lobes.

Genus Eighth. Illænus.

Body ovate oblong, contractile.

Head rounded in front, eyes small, in the temples, very remote.

Abdomen with from 9 to 10 articulations, trilobate.

Tail expanded as large as the head.

Genus Ninth. Ampyx.

Body very short, contractile.

Buckler large, triangular, gibbous; eyes not remarkable.

Abdomen short, articulations few (6?), trilobate.

Tail expanded, not so large as the head.

Professor Dalman has two other genera, which he calls Olenus and Battus, the first is the Paradoxides, and the second the Agnostus of Brongniart.

In the 8th Volume of Annales des Sciences Naturelles there is a highly valuable paper "Sur les Trilobites et leurs gisemens," by the Count Rasoumowsky, in which he describes some new trilobites from Russia; the one which he has figured and described as a Calymene from Tzarsko-Selo, undoubtedly belongs to a new genus, very near to the Isotelus. The middle lobe is visible or naked through its whole extent, and the lateral lobes near the tail are covered with a thick cuticular membrane. This genus we propose to call Hemicrupturus, and may be thus characterized.

Genus Tenth. Hemicrupturus.--Green.

Body contractile.

Buckler oculiferous and not lobate.

Abdomen trilobate, with 8 articulations.

Tail, costal arches covered, middle lobe naked.

The Asaphus expansus of Dalman, and several other known species may be arranged under this genus.

As Count Rasoumowsky has given no specific appellation to the fossil above alluded to, we propose to call it after his own name, Hemicrupturus Rasoumowskii. We examined the fine specimen from which our cast is taken in the cabinet of the Baltimore College, and for this favour we are indebted to the kindness of Dr. J. J. Cohen, one of the Professors in that rising institution.

The following list includes all the genera and species of the Trilobite Family, hitherto described as far as known to the author. It is taken from De La Beche's Manual of Geology.

NAMES. AUTHORS. LOCALITIES.

Calymene Blumenbachii, Al. Brong. Europe--U. States. Macrophthalma, do. Europe--U. States. Variolaris, do. Europe. Tristani, do. Europe--U. States. Bellatula, Dalman. Europe. Ornata, do. Europe. Verrucosa, do. Europe.

Calymene Polytoma, Dalman. Europe. Artinura, do. Europe. Sclerops, do. Europe. Schlotheimi, Brown. Europe. Latiferus, do. Europe.

Asaphus Cornigerus, Al. Brong. Europe. Caudatus, do. Europe--U. States. Hausmanni, do. Europe--U. States. De Buchii, do. Europe. Brongniartii, Deslongchamps. Europe. Extenuatus, Wahlenberg. Europe. Granulatus, do. Europe. Expansus, do. Europe. Crassicauda, do. Europe. Angustifrons, do. Europe. Heros, Dalman, Europe. Platynotus, do. Europe. Frontalis, do. Europe. Læviceps, do. Europe. Palpebrosus, do. Europe. Sluzeri, do. Europe.

Ogygia Guettardii, Al. Brong. Europe. Desmaresti, do. Europe. Wahlenbergii, do. Europe. Sillimani, do. Europe--U. States.