I20 AN INTRODUCTION TO THE STUDY OF FOSSILS 



1. Sketch a portion of a colony, indicat- 

 ing a hydrotheca and its aperture. 



2. What is the chemical composition of the 

 fossil at present ? When living ? 



3. How do you account for the great 

 abundance and the fragmentary condition of 

 these colonies, as for example in the Utica 

 shale ? 



Fig. 43. — The grap- 

 tolite, Climacograp- 

 tus typkalis Hall 

 (X 7), from the Utica 

 shale of New York. 

 Only the end of the 

 colony bearing the 

 sicula is.) is here 

 shown. (From 

 Ruedemann.) 



Monograptus (Fig. 44). Silurian. 



Cups (hydrothecae) arranged in one row 

 along the straight or curved stem (whence 

 the name from the Greek monos, one). The 

 virgula can be seen as a ridge extending 

 the length of the colony | 

 opposite the cups. M. clin- 

 tonensis is an abundant and 

 well-preserved species in 

 the Silurian (Clinton) 



shales of New York State. 



1. Sketch portion of a colony, enlarging 

 it three times. Label a hydrotheca and its 

 aperture, the virgula, the position of the 

 central canal. 



2. Sketch the probable appearance of the 

 soft body of a polyp with tentacles expanded. 



3. Briefly describe the probable digestive 

 system of Monograptus. 



4. How was the hydrotheca formed ? 



5. What use did this cup subserve ? 



6. What is the significance of the name 

 Monograptus ? 



7. Give reasons for placing this under the 

 Coelenterata rather than under the Porifera. 



Order 2, LeptolincB. — Hydrozoa which dur- 

 ing one generation are fixed to some foreign 

 object, as seaweed, and grow by budding, 

 very much like a plant. These bud off por- 



'A 



Fig. 44. — The grap- 

 tolite, Monograptus 

 clintonensis Hall, 

 from the Clinton 

 formation (Middle 

 Silurian) of New 

 York. Side views. 

 A , natural size (from 

 Hall) ; B, an en- 

 largement of six cups. 

 (From Ruedemann.) 



