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The family may be divided into throe groups, according to the 

 form of the tail. 



I. The tail obliquely truncated with a Jtat superior disk. 



1. Silououka. Disk oblong, covered with separate, two or four 

 keeled scales. 



2. Uropeltis. Disk circular, covered with a single tubercular 

 plate. 



II. The tail subtruncate ; end convex, rounded, covered with a 

 single horny tubercular shield. 



3. Mytilia. Caudal shield many-keeled ; nose more or less 

 acute. 



1. Siloboura Elliott. 



2. .Ify/ilia Tcmpletonii. 



3. Plectrum* Perrotetti. 



Mytilia unimaculata. 

 Mytilia melanogaster. 



III. Tail oblong, compressed, covered with separate 3-keeled settles ; 

 tip covered with o Small romprcs.sed cup-liko spinosp shield. 



4. Maudia. 



Instead of this family being characterized by the tail being "cylin- 

 drical, obliquely truncated above," it ought t<> be described as tail 

 cylindrical or compressed, covered with keeled scales, which are 

 separate or more or less united into a horny shield, — the scales on 

 the tip of the tail being always united nnil many-keeled. 



