406 GEOLOGICAL SUCCESSION OF ANIMALS. 



Marsupialia, and having some resemblance to the opossum 

 (fig. 385). 



Fig. 385. Jaw of the Thylacotherium. from Stonesfield. 



6/5. The department of mollusca is largely represented 

 in all its classes ; Some of the most common forms are sketched 

 in fig. 386. The peculiar types of the primary age have 

 almost disappeared, and are replaced by a greater variety of 

 new forms. Of the brachiopoda only one type, namely, that 

 of the Terebratula (10), is abundant. Among the other bi- 

 valves there are many peculiar forms, as Gryph&a (1 and 2), 

 Cardium (4), Trigonia (5), Goniomya (6), and Gervillia (8). 

 The gasteropoda display a great variety of species, and the 

 genus Nerin&a (11) is an abundant form. The Cephalopoda 

 are very numerous, among which the Ammonites (9) are the 

 most prominent. There are also found, for the first time, the 

 representatives of the cuttle-fishes, under the form of Belem- 

 nites, an extinct type of animals, with an internal chambered 

 shell, protected by a sheath, and terminating in a conical 

 body somewhat similar to the bone of the Sepia, and which is 

 commonly the only preserved part. 



676. The variety is not less remarkable among the 

 radiata. There are to be found representatives of all the 

 classes; even traces of jelly-fisheshavebeenmadeoutinthe slates 

 of Solenhofen, in Bavaria. The' polyps were very abundant 

 at that epoch, especially in the upper stages, one of which, 

 from this circumstance, has received the name of Coral-rag. 

 Indeed, there are to be found whole reefs of corals in their 

 natural position, similar to those which are to be seen in the 

 islands of the Pacific. [Among the most remarkable types 



