114 SYSTEMATIC PALEONTOLOGY 



The otolites of C3'clostomes and cartilaginous fishes consist of irregu- 

 lar and loosely united aggregations of lime carbonate; those of Teleos- 

 tomes, on the other hand^ are dense porcellanous bodies composed of 

 microscopic crystals of calcite, excellently adapted for fossilization. The 

 proportion of calcite frequently amounts to 98 per cent of the whole, 

 and the organic matter rarely exceeds 4 per cent. Although extremely 

 variable in form and size, nothing can be predicated from these char- 

 acters as to the proportions of the complete fish. The sculpturing of 

 the external surface, however, has been found fairly distinctive for cer- 

 tain families; for instance, it is more or less tuberculose among the 

 Gadidae, Sciaenidae, etc., and radially folded among the Percidae 

 and Spaeidae. 



Otolites are secreted in a few definite regions of the auditory appa- 

 ratus. A small one, termed by Koken the lapillus, is formed in a por- 

 tion of the labyrinth known as the "vestibule" or utriculus; another 

 (asteriscus of Koken) occurs in the posterior prolongation of the otolite- 

 sac (sacculus), and the principal ear-stone in the center of the sac proper. 

 The principal otolite {sagitta of Koken) occupies a constant position 

 with reference to the investing sacculus, partaking of its shape and 

 being attached to its inner wall; and accordingly it is capable of being 

 precisely oriented, even when found in the detached fossil condition. 

 That is to say, a dorsal and ventral, anterior and posterior, and inner 

 and outer side are almost always to be recognized, as well as the side of 

 the head to which it belongs. But on the other hand the configuration, 

 and in the opinion of some excellent authorities, even the surface mark- 

 ings of fish otolites are dependent on the variable form of the enclosing 

 membranous sac, and are by no means constant within specific or even 

 generic limits.^ 



' " Hasse hiilt aiich die Form der Otolitben fiir unwichtig, als ein mit der Form 

 des Sacculus sich anderndes Moment. . . . Die Gestalt der Otolithen ist allerdiugs in 

 gewissen Grenzen variabel, in Zusammenhange mit den individuellen Scliwanlvungen 

 der Sacculus-Form, welcher sie sich anpasst. Audi ist das Wachsthum vorvviegend 

 auf die iiussere Seite angewiesen, welche frei im Sacculus liegt ; .... dementsprechend 

 ist das Wachsthum der iiusseren Seite unregelmiissiger, und gerade die auf die Sculptur 

 derselben sich griiudenden Merkmale . . . erwiesen sich ofters als ungeeignet, well sie 

 sich durcli Vergrosserung des Gehiirsteines zu leicht verwischen." — E. Koken, Ueber 

 Fisch-Otolithen etc. (Zeitxchr. d. d. geol. Gcs., vol. xxxvi, 1884, p. 518). 



