PLATE XVIII 
Fics. 1 anp 2. Orestias luteus Valenciennes, 16095, part, 172 mm., L. 
Umayo. 
Fia. 3. Orestias olivaceus Garman, 3946 MCZ, 84 mm., L. Umayo. 
Fic. 4. Radiograph of one of the shorter species, Orestias agassizii, 105 
mm. to caudal basis. 
Fia. 5. Radiograph of a longer species, Orestias pentland?, 172 mm. to 
caudal basis. 
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