30 KANSAS CITY REVIEW OF SCIENCE, 



Gryphoza dilatata— the former, Ostrea, is said to have been the progenitor of the 

 common oyster, which bivalve is held in such great demand. The remains of 

 Gasteropods, Ammonites Humphreysia?ms — similar to the Triassic fossils — are met 

 with occasionally. 



Of the sub-kingdom of Articulates, specimens of various worms, crusta- 

 ceans, spiders, &c, are found. A crustacean, closely resembling the Eryon Arc- 

 tiformis of the Oolite, is occasionally seen. This curious looking animal had a 

 body something like our crawfish of to-day — with formidable pincers and a hard, 

 bony-cased head. None of the larger class of animals of the Jurassic — Ichthyo- 

 saurus, Plesiosaurus and Pliosaurus, etc., are found, but, in connection with this 

 period, I will describe briefly the above denizens of the Jurassic Sea. The Ich 

 thyosaurs, (the name, from the Greek, signifying fish-lizard,) were gigantic ani- 

 mals, ten to forty feet long, having paddles somewhat like the whale. It had a 

 long head, whose lower portion of which was armed with formidable-looking jaws, 

 containing, in some species, two hundred stout, conical, striated teeth. This ter- 

 rible creature also had an eye of enormous dimensions — in one species the orbi- 

 tal cavity being fourteen inches, in its longest direction — this eye, also, had a 

 peculiar construction, to cause it to act both as a telescope and microscope, thus 

 enabling the animal to descry its prey deep down in the water, and in the night 

 as well as day. The length of the jaws was sometimes more than six feet. Its 

 skin was naked, some of it having been found in a fossil state ; its habits were 

 carnivorous ; its food, fishes and the young of its own species — some which it 

 must have swallowed — were several feet in length. The Plesiosaur (the name 

 meaning allied to a Saurian) had a long, snake-like neck consisting of from 

 twenty to forty vertebrae, a small head, short body, with paddles similar to the 

 Ichthyosaurus. Its paddles were proportionally larger than its prototype, no doubt 

 for the purpose of greater speed in the pursuit of its prey. It was an inhabitant 

 most probably of the shallow arms of the Jurassic Sea, where it probably used its 

 long neck for seizing fish beneath, and perhaps flying reptiles above the water — 

 of which there were many kinds. 



Leaving the Jurassic, we enter the Cretaceous (Chalk) period, which is the 

 closing era of the Reptilian Age. It is remarkable for the number of genera 

 of mollusks and reptiles which end with it; and also for the appearance during its 

 progress of the modern types of plants. This period is divided into two epochs — 

 Earlier and Later Cretaceous. The rocks of this period "occur (i) at intervals 

 along th^ Atlantic border, south of New York, from New Jersey to South Caro- 

 lina ; (2) extensively over the States along the Gulf border; thence bending 

 northward along the Mississippi Valley, beyond the mouth of the Ohio, over 

 what was then a great Mississippi bay ; (3) through a large part of the western 

 interior region, over the slopes of the Rocky Mountains, from Texas northward 

 to the headwaters of the Missouri, and westward through Dakota, Wyoming and 

 Utah Territories and the State of Colorado; along farther west, through some 

 parts of the Colorado Valley, but not over the plateau between the Sierra Ne- 



