TRIASSIC SYSTEM. 49 



comb on the outer edge. The perch, and many other existing genera, are 

 of this order, which contains but few fossil forms. The order of Cyclodi- 

 ans (from the Greek, kuklos, a circle) is characterized by having scales 

 which are smooth and simple at the margin, as in the herring, salmon, &c. 

 When the vertebral column is prolonged into the caudal fin, tne tail is 

 he'terocercal; when the vertebral column t rminates where the tail is given 

 off, we have the homocercal tail, as in most of the recent fishes. 



In this same formation we also find Spi'rifers (Jig. 58), and 

 Productus (figs. 59, fiO), and especially the Productus aculea'tits 

 (Jig. 59), which, under the name of gry'phites acuhdtm, has 

 been regarded as characteristic of it in Germany ; and sometimes, 

 in consequence, the zechstein is called gryphltenkalk, which, on 

 this account, has heen confounded with the lias. Other mollusks, 

 as well as the remains of encri'nites, which seem to be the same as 

 those of the carboni'ferous limestone, are also found. 



Fig.5S.Sfji'rifer Fig. 59. Productus Fig. 60. Pro- 



undula'tus. aculea'tus. ductus calvus. 



26. Next in order is a layer, known as the sandstone of Vosges, 

 which lies either on the red sandstone or magnesian limestone ; 

 or, when these strata are wanting, on some other more ancient rock. 

 After the formation of the several portions of the crust of the globe 

 just mentioned, geological convulsions again occurred, and, as it 

 appears, the mountains of Vosges, the Black Forest, &c., were 

 elevated about the same time. After this movement, new deposits 

 were formed around the base of the hills, constituting the Trias 

 System of French and German geologists, so named because it is 

 composed of three kinds of rocks. 



27. The TRIAS or TRIA'SSIC SYSTEM (or upper new red sand- 

 stone of the English) consists of: 



1. Bunier Sandstein, (gres bigarre of the French), a quartzose 

 sandy deposit, which usually forms the base of J;he system, both in 

 France and Germany. 



2. Muschelkalk, (shell-chalk), a well-marked and highly fossili'- 

 ferc as limestone, rarely absent in the continental series, but never 

 found in England. 



3. Keuper, a singular group of sandy marls, of variegated 

 colours, frequently containing salt and gypsum, and remarkable 

 for numerous fossil vegetable remains. 



28. The BUNTER SANDSTEIN, or Gres Bigarre, is a fine-grained, 



26. What is the relative position of the Vosges sandstone ? 



27. What is the trias, or tria'ssic system ? 



5 



