6.1 AVICULA. POSIDOXIA TRIGONIA ENCRINI'J'htS. 



Fio-,63 



The genus A'vicula (Jig. 63) belongs to the 

 division of bivalve shells, and the fossil species, 

 a great many of which are known, resemble the 

 pearl oyster (A'vicula Murgaritifera}. 



The genus Posido'nia, (Jig. 64), (from the 

 Greek, posfidon, Neptune), also belongs to the 

 bivalves, and is found in the lower part of tho 

 carboni'ferous series. 



Fig. 65. Trigo'nia vvlga'ris. 



The genus Trigonia, (fig 65 from the Greek, trigonos, three-cornered), 

 belongs to the family of ostracea ; the only living species known inhabits 

 the seas of New Holland. 



Fig. 66. Encri'nites monilifor'mis. 



The Encri'nites, (Jig. 66 from the Greek, krinon, a lily), belong to the 

 family of Echi'noderms. The skeleton of this animal is said to consist 

 of not less than 26,000 separate pieces. The body of the lily-encrinite was 

 supported on a long and nearly cylindrical column, attached to a rock or 

 some nard substance at the bottom of the sea by an enlargement of its base. 

 This column was made up of a vast number of joints, through which was 

 an aperture, descending from the stomach of the animal to the base of the 

 column. 



32. The KEU'PER (a German word) is the name given to 

 the uppermost division of the tria'ssic system, and is often ap- 

 plied to the upper part of the new red sandstone formation. This 



32. What are the characters of the Keuper formation ? What organic 

 remain? are found in the Keuper series ? 



