of the shell or of internal fillings or external molds. They generally range 

 in size from a fraction of an inch to a few inches in length and width. 



Cephalopods 



Cephalopods are among the most highly developed mollusks. Squids, 

 octopuses, cuttlefish, and the pearly nautilus are living representatives of 

 this class which are abundantly represented as fossils. The calcium carbonate 

 shell possessed by ancient forms has essentially the form of a slender cone 

 which may be straight, curved, or coiled. Whether loosely to tightly coiled, 

 it is almost always in a flat spiral. 



The animal occupied only the end portion of the fossil shell. It sealed 

 this "living chamber" off from the rest of the shell by transverse partitions 

 called septa. The line of junction of the septa with the inner surface of 

 the shell wall is called the suture. In most fossil cephalopods the outer shell 

 has been eroded away, exposing the characteristic kinds of sutures. These 

 suture lines and the presence of a small tube running through the septa 

 connecting the chambers are distinguishing features of cephalopods. 



Straight and coiled shelled cephalopod fossils are found in the shales 

 and limestones of Western New York. The cover portrays a restoration 

 of the nautiloid cephalopod Nephritic eras. Its shell can be found locally. 



Annelids 



Annelid worms are represented by fossils of various forms including 

 tooth-bearing jaw parts, trails, castings, and tubes. The worm jaws, called 

 scolecodonts, show considerable range in shape, size, structure, and number. 

 These microscopic or near-microscopic fossils are usually composed of chitin 

 and are recognized by their black, glossy, opaque appearance. 



Fossil worm tubes are minute straight or coiled snail-like forms which 

 can be found cemented to the surface of other fossils. The tubes are often 

 ornamented with ridges, spines, and nodes. 



Fossil worm borings or trails are occasionally found but are generally 

 difficult to recognize. Arthrophycus, a fossil found in the rocks of the 

 Niagara Gorge, is believed by some paleontologists to be worm tubes; others 

 consider it a primitive plant. 



Conodonts 



Conodonts are minute, toothlike, transparent, or translucent fossils. 

 Conodonts can be distiguished from fossil worm jaws or scolecodonts by 

 their smaller size, calcium phosphate composition, translucent nature, and 

 pale amber to dark brown color. 





I 





CONODONT 



EURYPTERID Eurypterus lacustris 



