FOSSIL REMAINS TRILOBITES. 



supported on movable peduncles, as the crab and lobster*, and those with 

 eyes fixed ; the extinct order of trilobites belongs to the last. 



The Caly'mene. Blumenbachii (Jig. 4, No. 3) is named after the celebrated 

 German naturalist Blumenbach ; the generic name, caly'mene (formed from 

 the Greek kekalumene, concealed) was devised to express the obscure nature 

 of this genus of trilobites. It is found- expanded, with its under surface 

 attached to and blended with the limestone, or coiled up. The head is large, 

 convex, rounded in front, with a broad border, and divided into three lobes 

 by two longitudinal depressions. It has two compound eyes with numerous 

 facets, situated at the back of the head remote from each other. This spe- 

 cies is from one to four inches in length. Mantell. 



" It is a curious fact," says Mr. T. A. Conrad (Palaeontologist, State of 

 New York, 1838), "that, whilst the Caly'mene Blumenbachii ceased to 

 exist in New York after the final deposition of the Trenton series, it escaped 

 into remote seas and lived in the era of the Dudley limestone." 



In another genus, A'saphus (from the Greek asaphcs, obscure), the cara- 

 pace is wide and much depressed (Jig. 4, Nos. 1,2); the middle lobe distinct, 

 the cephalic portion rounded in front, and terminating posteriorly in a sharp 

 process on each side. The eyes are compound, and each contains four hun- 

 dred spherical lenses. Some kinds of A'saphus have remarkably long, 

 pointed, caudal appendages, or tails, (Jig. 4, No. 1). Some American species 

 of this group are eighteen inches in length. Mantell. 



31. Besides the trilobites, the remains of other animals are found 

 in the Cambrian and Silurian Systems. They mostly belong to 

 the division of brachiopod mollusks. Among those which are 

 regarded as characteristic of the Silurian System are the Orthis 

 orbiciilaris (fig. 5), Orthis testudinaria (Jig. 6) : the orthis is a 

 circular shell with a striated surface, and long, narrow hinge; 



Fig. 5. Orthis orbicularis. big. 6. Orthis testudinaria. 



the Orthoceras (Jig. 7), (from the Greek orthos, straight, and keras 

 horn) ; the Luiiuites (Jig. 8), of large dimensions ; the Productut 



Fig. 1. Orthoceras conica. 



Fig. 8. Lithuites giganleut. 



31. Name some of the fossils found in the Cambrian and Silurian Syt 

 terns. To what division of the animal kingdom do these fossils belong 7 



