CAKBOKTEEROTTS SYSTEM. 209 



so than they are in the Kinderhook beds. In the npper 

 division their abundance is so largely increased that they 

 form a very conspicuous feature of its palaeontology; and 

 taken together, with the abundance of similar remains in the 

 Keokuk limestone, these vertebrate relics constitute a promi- 

 nent character of the palaeontology of the whole group of 

 Sub-carboniferous rocks of Iowa. 



Articulates. Remains of Articulates are rare in this 

 formation, and, so far as yet discovered, they are confined to 

 two species of trilobites, both belonging to the genus, 

 Phillipsia. One, if not both of these, is specifically different 

 from the two species found in the Kinderhook beds. 



Molltjsks. Fossil shells are very common in this formation, 

 but they constitute a much less prominent palseontolgical 

 character of it than they do of some of the other formations 

 of the group. The classes Gasteropoda, Pteropoda, BracMo- 

 poda, Lamellibranc7iiata and Polyzoa are all represented; 

 but thus far no Ceplialopods nor any specimens of the 

 Heteropod division of Gasteropoda have been recognized in 

 the true Burlington limestone. 



Radiates. The two lowest classes of the sub-kingdom 

 Radiata, are represented in the genera ZapJirentis, Amplexus 

 and Syringopora, while the remains of the highest class — 

 Echinoderms— are found in both divisions of the formation, 

 in the most extraordinary profusion. A few of these are 

 Asteroids and Blastoids, but Crinoids are more abundant 

 than all other Radiates. The number of species of Crinoids 

 alone that have been obtained from the Burlington limestone 

 of Iowa and the adjoining States, is now known to reach 

 more than three hundred.* 



* At Burlington several persons have made important collections of fossil Echino- 

 derms ; but the collection made there by Mr. Charles Wachsmuth, witnin the last 

 twelve years, is most remarkable, and is without doubt the most extensive collection 

 of the kind in the world, made at one locality. Mr. Wachsmuth has furnished me 

 with the following summary of his collections made at, and in the vicinity of Bur- 

 lington alone, from both divisions of the Burlington limestone: 



Species, included in 40 Genera. 



4 



3 « 



2 



n 



Orinoidce 



338 



Blastoidce 



17 



Echinidce 



6 



A.steroidoe 



4 



Ophiuridce 



1 



Total Species 



366 



•50 Genera. 



