As additional features of the subclass may be mentioned the absence of a corpus callosum connecting the right and left hemispheres of the brain,' and of a fossa in the septum between the two auricles of the heart.
They were placed by Marsh in a distinct subclass of birds,Odontornithes.
We conclude, therefore, that the primitive stock of the former subclass became early differentiated from that of the latter.
Instead of recognizing, as before, a subclass in the Ratitae of Merrem, Nitzsch now reduced them to the rank of an order under the name " Platysternae," placing them between the " Gallinaceae " and " Grallae," though admitting that in their pterylosis they differ from all other birds, in ways that he is at great pains to describe, in each of the four genera examined by him - Struthio, Rhea, Dromaeus and Casuarius.
Pp. 161, 162) for their reception a " subclass" Odontornithes and an order Ichthyornithes.
Marsh states that he had fully satisfied himself that Archaeopteryx belonged to the Odontornithes, which he thought it advisable for the present to regard as a subclass, separated into three orders - Odontolcae, Odontotormae and Saururae - all well marked, but evidently not of equal rank, the last being clearly much more widely distinguished from the first two than they are from one another.
Thus instead of contenting himself with terms that had met with pretty general approval, such as class, subclass, order, suborder, family, subfamily, and so on, he introduced into his final scheme other designations, " agmen," " cohors," " phalanx," and the like, which to the ordinary student of ornithology convey an indefinite meaning, if any meaning at all.
LAMPREY, a fish belonging to the family Petromyzontidae (from r rpos and Ww, literally, stone-suckers), which with the hag-fishes or Myxinidae forms a distinct subclass of fishes, the Cyclostomata, distinguished by the low organization of their skeleton, which is cartilaginous, without vertebral segmentation, without ribs or real jaws, and without limbs.
The choice is open to maintain the last as an independent subclass, and to follow Claus in calling it the Leptostraca, or to introduce it among the Malacostraca as the Nebaliacea, or with Packard and Sars to make it an entomostracan subdivision under the title Phyllocarida.
195).5 The kiwis form a group of the subclass Ratitae to which the rank of an order may fitly be assigned, as they differ in many important particulars from any of the other existing forms of Ratite birds.
GERANIACEAE, in botany, a small but very widely distributed natural order of Dicotyledons belonging to the subclass Polypetalae, containing about 360 species in 11 genera.
Brit., 9th ed., 1883) placed them under the name Isopleura as a subclass of Gastropoda.
Crystals of blende belong to that subclass of the cubic system in which there are six planes of symmetry parallel to the faces of the rhombic dodecahedron and none parallel to the cubic faces; in other words, the crystals are cubic with inclined hemihedrism, and have no centre of symmetry.
The second subclass, Gamopetalae, includes 9 series and culminates in those which show the most elaborate type of flower, the series Aggregatae, the chief representative of which is the great and wide-spread order Compositae.
Haeckel established the subclass Saururae, containing solely Archaeopteryx, in opposition to the Ornithurae, comprising all the other birds.
It has been proposed by Maas to divide the entire subclass Acraspeda into A, Charybdaeida and B, Acraspeda typica.
There can be little doubt that they should be regarded as types of as many orders - Struthiones and Rheae - of the subclass Ratitae.