162 Mil. E. T. HIGGmS ON THE OTOLITES OE FISH. 



posited by a dialytic process, a thin section showing layer upon 

 layer in strict accordance with such an origin." 



Such is unquestionably the case with some of the Gradidae, and 

 may perchance be the character of the family ; but in by far the 

 largest number offish the structure more nearly resembles that of 

 bone. 



The otolites amongst osseous fish may be said to be three in 

 number on each side, as the exceptions to the rule are very rare. 

 During the examination of more than 3700 fishes, I have only 

 noticed five instances to the contrary. In three they were alto- 

 gether wanting on one side, and normal on the other ; these were 

 in a Perch, Eoach, and Salmon, fish possessing otolites sufficiently 

 large to be readily found, if they existed. The fourth instance 

 occurred in a Carp Bream (Ahramis hrama) : the otolites on one 

 side were quite normal in size, shape, and number ; but on the 

 other side it (for there was only one) was cartilaginous and ab- 

 normal. The fifth occurred in Synaplwhranchns Kaupii, the ante- 

 rior and posterior otolites being represented by numerous minute 

 crystals imbedded in a tough membrane. 



Though amongst my series of otolites a few examples of the 

 three are exhibited, yet the only one of scientific interest is the 

 central or largest, as the other two, which are usually placed 

 superiorly and posteriorly, though occasionally lying on the cen- 

 tral, or with it (as in the Cyprinidse) forming a chain of bones, are 

 in the majority of fish so small as to be with difficulty found, and, 

 when found, of so little use for the purpose of scientific identifica- 

 tion that I will almost pass over them, merely stating that the 

 superior is usually more globose, smaller, and rather porcellanou^, 

 and varies considerably in form, being rounded, triangular, stellate, 

 or hastate. The posterior otolite is usually semitransparent, 

 somewhat resembling fish-bone in appearance, rounded, quadrate, 

 semilunar, in one instance resembling the stapes wanting its base, 

 and generally pectinated. Althovigh many thousands of fossil 

 otolites have been examined by me, no specimen that could be re- 

 ferred to either of the above has yet been met -with. 



The central or largest otolite is crystalline in structure, por- 

 cellanous, closely resembling beautifully pure enamel in appear- 

 ance, very brittle, owing to the imperfect cohesion of its atoms, 

 easily rubbing down into almost impalpable powder. In spirit 

 the porcellanous appearance is after a time destroyed, and the 

 otolites become, to a certain extent, chalky and opake. This 

 otolite is concave above, convex and grooved below^, indented or 



