

While the animals possessed a hard dorsal covering, their lower surface 

 was not similarly protected. To protect themselves from enemies the trilo- 

 bites curled up into balls. Fossils may be found of curled up trilobites. 



Trilobite fossils are often fragmentary because the trilobite shell is 

 so differentiated and the sections easily separated. A commonly found 

 trilobite in the rocks of Western New York is Phacops rana. It is charac- 

 terized by large popping eyes and an oval-shaped body of many segments 

 Dalmanites is a trilobite with a thorax of eleven segments and a tail which 

 is often large and pointed. 



Ostracodes 



Ostracodes are usually microscopic or almost microscopic crustaceans, 

 the same class of animals that includes lobsters and crabs. The oval or 

 bean-shaped shells of ostracods are composed of two valves hinged at the 

 top. The shells may be smooth and rounded or marked by various structures 

 such as lobes, pits, spines, or nodes. 



Fossil ostracodes are common in some of the rock formations of 

 Western New York but may be difficult to find because of their small size. 



Echinoderms 



Echinoderms include animals well known today, such as the star-fishes, 

 as well as forms known only as fossils. The echinoderm shell is in the form of 

 calcium carbonate plates which form mosaic patterns covering the body. 

 Many fossil echinoderms were attached to some foreign object or to the 

 sea bottom by a flexible jointed stem. 



Cystoids 



Cystoids, the most primitive echinoderms, possess a body of irregularly 

 arranged plates which result in a fossil of saclike indefinite form. The body 

 plates in most cystoids are five-sided or polygonal in shape and are per- 

 forated by pores or fissures. 



A cystoid found in Western New York is the oval shaped Caryocrinites 

 ornatus. It is characterized by pores radiating from the center of the indi- 

 vidual plates. These pores form rhombic-shaped designs covering the fossil. 



Blasfoids 



Blastoids are extinct echinoderms with a symmetrical, often bud-like, 

 body usually less than an inch in diameter. Their bodies are encased in 

 shells composed of thirteen principal plates firmly knit in definite positions. 

 There are five food grooves running downward from the top of the blastoid. 



A representative Western New York blastoid, Nucleocrinus, is of about 

 the size and shape of a small olive. The five food grooves are very narrow 

 in this particular species. 



TRILOBITE Phacops rana BLASTOID Nucleocrinus CRINOID STEMS 



