34 



OHIO FOSSILS 



Fig. 31 



ORDER FORAMINIFERA . In this order the shell is commonly 

 of calcium carbonate and made up of a number of microscopic cham- 

 bers. Some of the Foraminifera are very abundant in the sea and the 

 accumulation of their shells forms a limy ooze on the bottom. Some 

 50,000,000 square miles of the sea floor are covered to an unknown 

 depth with a layer of Globigerina ooze, named after the genus which 

 is its commonest constituent (fig. 31). During early Tertiary time, 

 shells of the genus Nummulites accumulated in the same way in the 

 Mediterranean area. Tertiary limestones containing abundant 

 Nummulites were used to build the Pyramids of Egypt. Foraminifera 

 are almost exclusively marine, that is, they live only in the sea; a 

 single family lives in fresh water. They have been recorded doubt- 

 fully from the pre-Cambrian and are certainly known from the Cam- 

 brian to the present. 



The Foraminifera most easily seen in Ohio rocks are the fusulines, spindle-shaped shells 

 not more than three eighths of an inch long. Some of our Pennsylvanian limestones contain 

 abundant fusulines. 



ORDER RADIOL ARIA . These protozoans build their shell of silica. They are not cham- 

 bered like the Foraminifera but instead appear under the microscope as globes and pyramids of 

 glass pierced by numerous holes and ornamented with spines. They are exclusively marine and 

 have been recorded doubtfully from the pre-Cambrian, certainly from the Cambrian to the pre- 

 sent. They have not as yet been recorded from Ohio rocks. 



Phylum Porifera 



These are the sponges, which look like plants but are really many-celled animals. The 

 cells are loosely organized and have little specialization. The sponges secrete a skeleton which 

 may be either mineral (calcium carbonate or silica) or organic (spongin, a substance allied to 

 silk). The skeleton, when it consists of mineral matter, is made up of tiny elements called 

 spicules which are shaped like rods, clubs, disks, and other forms too complex to describe here. 

 Sponges may be preserved entire (fig. 32) or the spicules may be scattered after death and 

 preserved individually or in groups. Sponges are found both in the sea and in fresh water. Their 

 geologic range is from the pre-Cambrian to the present. Sponges have been found in most of the 

 Paleozoic rocks of Ohio but they are not common. 



Phylum Coelenterata 



Fig. 32 



In this phylum, the many cells of the body are specialized and 

 there is a definite body cavity, that is, a space between the body wall 

 and the lining of the digestive cavity. The space is filled with a fluid 

 which contains many dissolved substances which nourish the body cells. 

 The phylum includes the hydroids, corals, jellyfish, and two extinct 

 groups, the conularids and stroma toporoids. 



CLASS HYDROZOA . These are the hydroids which have a 

 circle of muscular tentacles around the mouth, with which they capture 

 their food, and stinging cells, with which they paralyze other animals 

 which they capture and eat. Few of them secrete hard parts capable of 

 preservation but fossil examples are known from the Lower Cambrian 

 to the present. The majority of the hydroids are marine but there are 

 a few freshwater forms. 



A curious group of fossils called Conularida (see fig. 235) were 



