Sub-Class Merostomata
Order Aglaspina, new order
Family Aglaspidæ Clarke
Genus Molaria, new genus
Genus Habelia, new genus
Genus Emeraldella, new genus
Order Limulava Walcott
Family Sidneyidæ Walcott
Genus Sidneyia Walcott
STRATIGRAPHIC DISTRIBUTION
The several genera of the four subclasses (with the exception of the group of malacostracans represented by genera other than Hymenocaris and the trilobitic genera Mollisonia and Tontoia) have approximately the known vertical range in the Cambrian noted in the diagram on page 156.
In addition to representatives of the subclasses Branchiopoda, Malacostraca, Trilobita, and Merostomata, mentioned in this paper, I have added in the table genera of the Merostomata that occur in the Lower Cambrian and Algonkian, respectively, and of the Ostracoda in the Lower Cambrian, in order to present an outline of the lowest known stratigraphic position of the five subclasses of Crustacea. With the exception of the Branchiopoda all of these are known to have representatives in later Paleozoic formations.
The subclass Merostomata is represented by Beltina[1] in the pre-Cambrian; by Amiella[2] in the upper part of the Lower Cambrian, by the latter genus and Habelia, Molaria, Emeraldella, and Sidneyia[3] in the Middle Cambrian Burgess shale; and by Aglaspis[4] and Strabops[5] in the Upper Cambrian.
The Phyllocarida is first known in the Lower Cambrian by Isoxys,[6] a genus that is represented in the Burgess shale. Hymenocaris is well distributed in the lower half of the Middle Cambrian and the order Hymenocarina continues on up into the Ordovician, Silurian, and Devonian.
- ↑ Bull. Geol. Soc. America, Vol. 10, 1899, p. 238.
- ↑ Smithsonian Misc. Coll., Vol. 57, No. 3, 1911, p. 28.
- ↑ Idem, p. 27.
- ↑ Sixteenth Ann. Rept. New York State Museum, 1863, pp. 181 and 182, pl. II, figs. 7-16.
- ↑ American Journ. Sci., Vol. 12, 1901, pp. 364-366, pl. 7.
- ↑ Tenth Ann. Rept. U. S. Geol. Survey, 1891, pp. 625 and 626, pl. 80, figs. 10 and 10a.
