74 SAN DIEGO SOCIETY OF NATURAL TISTORY 
RAYMOND (Percy E)—Continued 
Niobe, Symphysurus and Basilicus, are more primitive than Isotelus, Nileus, Ptychopyge, 
Hemigyraspis and Asaphellus. 
The author quotes Brogger’s studies on the hypostoma and his division of three dis- 
tinct types. 
Pointed behind, Megalaspis and Ogygiocaris. 
Quadrate, Niobe insignis. 
Extended behind into two long, large prongs, Asaphus, Isotelus, etc. He remarks 
under the Geologic range, that the Asaphids appear earlier in America and have a 
longer range than in any other country. 
The Cambrian, which liave entire hypostomas, consists of the genera Ogygopsis, 
Illaenurus, Symphysurus, Asaphellus, Hemigyraspis and Megalaspis. 
Ordovican, Beekmantown, the Asaphids are less varied as only Isoteloides and 
Nileus are present. 
In the Chazy, Isotelus, Isoteloides, Basilicus, Onchometopsus, Vogdesia and Nileus 
occur. 
In the Silurian, in the Lowville (Silurian) and Back River (Ordovian), the genera 
Onchometopus, Isotelus, Isoteloides, Basilieus and Vogdesia. 
In the Trenton there are, so far as is now known, only Isotelus and Isoteloides. 
In the Utica, Isotelus and Ogygites. 
In the Richmond, Isotelus, Onchometopus, Brachyaspis and probably Ogygites. 
The author uses dsaphus expansus as the type of the genus, which is characterized 
by its short, broad head, and pygidium from which all depressed borders are absent; 
by the rather prominent glabella, which expands towards the front and reaches the 
anterior margin; the large eyes; the course of the anterior portion of the frontal suture, 
which meets in a point in front of the eye; and the short pygidium, with narrow, well- 
defined axial lobe and smooth pleural lobes. G 
The genus is well developed in the Baltic Region. 
Under the heading of lines of development from the Asaphus, the author remarks 
that the variation in the Ordovician Baltic species seems to be in the direction of the 
obliteration of furrows on the surface; that is a further loss of evidence of original 
segmentation in cephalon and pygidium. 
Onchometopus differs from Asaphus, in having the glabella less marked, the axial 
lobe of the thorax wider, the thoracic segments flatter, the axial lobe of the pygidium 
less convex and without rings. 
Megalaspides, like Asaphus, with narrow axial lobe, expanding glabella, no de- 
pressed border on the pygidium, but with a narrow one on the front of the cephalon. 
Isoteloides, in which both the cephalon and pygidium have depressed borders. 
Isotelus, in which the axial lobe of the thorax is wide, the glabella and the axial 
lobe of the pygidium so ill-defined as to merge into the general surface of the head; 
therefore, both these smooth trilobites and species of Brachyaspis and Onchometopus 
are so like Isotelus, that the three genera can only be separated by their lines of de- 
velopment. 
Basilicus is a primitive genus, with forked hypostoma, with a strongly ribbed tail; 
the facial suture marginal in front, and the glabella strongly outlined and shows 
glabella furrows. 
The author remarks from Basilicus, Ogygites seems to have developed. 
Tromelin and Lebesconte, Assoc. Francaise, Adv. Sci., 1875, p. 33, use the new generic 
name of Ogygites for Brongniart’s Ogygia, it having been used for other genera in 
natural history. These authors use O. Desmaresti Brog. for the type, and include O. 
Brongniarti Rou. as a syn. The same authors refer Ogygia, the first species described 
under the genus by Brongniart, to the genus Asaphus. 
