. The Canadian naturalist and geologist. Natural history -- Periodicals. 44 Fossils of the Loiver Silurian Rods of Canada. whorls touch each other, but in those which are badly preserved, they are separate, as shewu in the above jQgure. This very interesting and often beautiful fossil is not found in neither the Trenton Limestone or Utica Slate, being confined to the Hudson Kiver group. Specimens have been procured at Toronto. In the Trenton Limestone there are several other species of this genus also very beautiful in their form and ; The generic name is from the Greek, Kurtos,
. The Canadian naturalist and geologist. Natural history -- Periodicals. 44 Fossils of the Loiver Silurian Rods of Canada. whorls touch each other, but in those which are badly preserved, they are separate, as shewu in the above jQgure. This very interesting and often beautiful fossil is not found in neither the Trenton Limestone or Utica Slate, being confined to the Hudson Kiver group. Specimens have been procured at Toronto. In the Trenton Limestone there are several other species of this genus also very beautiful in their form and ; The generic name is from the Greek, Kurtos, curved; and Liihos, stone. Ornatus, Latin, ornamented. Ambonychia radiata is one of the most common and characteristic fossils of the Hudson River group. In the system of classification given on page 31 , this and the next following species would rank among the AcepJi- ala or headless mollusks, of which the common clam-shells of our rivers and lakes are members. Fig 7 is the usual form, although it is frequently much smaller, and not so acute above. The surface is marked by from twenty- five to forty strong radiating ridges which are somewhat flattened upon the top and crossed by fine concentric striae. The grooves between are rounded on the bottom, and half the width of the ridges. The name Ambonychia is from the Greek Ambon, the boss of a shield, and Onyx, a claw in allusion to the rounded and claw shaped beak of some of the species, " Radiata,'' radiated. This fossil is abundant m the Hudson River group, but is not found in any other formation. It was originally called Pterinea carinata, and is often quoted by that name in different Fig. 8.—Modiolopsis modioloris. This fossil abounds in the Hudson River group, being characteristic of the central and higher portions of the formation. It is of an exceedingly variable form, and is thus described by Professor Hall : " Somewhat obliquely oblong-ovate, narrowed before, expanded and obliquely truncated posterio
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