OTION. 



are semilunar, are placed, one on each side of the lower 

 part of the aperture;* one, which is exceedingly minute,, 

 and not always testaceous, according to Leach, hut some- 

 times corneous, is placed on the back; the two others, 

 which are also very minute, are placed one on each side 

 of a little fissure at the top of the aperture : according to 

 Leach, these also are sometimes horny. 



Several recent species of this very curious genus are 

 described; we are of opinion that they cannot fairly be 

 looked upon as natives of our coasts, though they have 

 been found on them, because we think they have been 

 introdut'ed from foreign climates; we have seen two 

 fine groups, attached to specimens of Coronula IMadema, 

 preserved in spirits in the Museum of the Royal College of 

 Surgeons ; from one of these, Ellis's figure published in the 

 Philosophical Transactions" for 17^8, appears to have 

 been taken, and the Coromda Diadema is known to be a 

 parasite on the South Sea Whales. 



This Genus is only found in a recent state. 



Fig. 1. Otion Cuvieri. 



2. Tlie lateral testaceous valves 



3. The dorsal valve. 



4. The terminal valves. 



* We must observe that in this Genus, Lamarck says the aperture through 

 which the tentacula pass is lateral, but speaks of it as anterior in Cinaras ; tof 

 our view its situation in both is perfectly analogous j indeed we consider it a« 

 anterior in all thie Cirripedes. 



