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THE "LAPILLUS" IN FISHES. 

 By Colonel C. E. Shepherd (Indian Army). 



"Lapillus" is the name given by scientists to that otolith 

 found in the recessus utriculi portion of the ear-labyrinth of 

 teleostean fishes. Up to the present time no special notes seem 

 to have been published regarding this stone. The " Astericus " 

 was treated of in the ' Zoologist ' for February, 1910 ; and many 

 sagittae are shown, and their peculiarities, when out of the com- 

 mon, pointed out, in the ' Zoologist ' for August, 1910 ; in the 

 March and April numbers for 1914, and January, 1915. In the 

 illustrations of the four latter papers many figures of lapilli are 

 incidentally shown, but this stone is, as a rule, so small that 

 nothing definite is seen ; some enlarged drawings may enhance 

 interest in them. The purpose they fill and the need of their 

 presence in the auditory labyrinth of a fish is at present inde- 

 terminate. They have a variety of forms ; Mr. Higgins,* who 

 made a collection of otoliths about the middle of last century, 

 calls the lapillus " the superior otolite " (sic), because it occupies 

 a spot in the brain-cavity of a fish a little above the other 

 otoliths. He says of the lapillus that it is " usually more 

 globose, smaller "(compared to the sagitta, he means), "and 

 rather porcellanous, and varies considerably in form, being 

 rounded, triangular, stellate, or hastate." To which may be 

 added, some resemble closely the shape of a seed in the grape. 

 The place of the lapillus in the Acipenserida, as exemplified in 

 Acipenser sturio, is taken by otoconia (ear-dust) instead of a 

 solid otolith (ear- stone) ; the otoconia t being separate crystals 

 of carbonate of lime. 



In the present paper it is as well to take first those fishes 

 that have a palpably large lapillus. The first family, then, to 

 be reviewed is the 



CeRATODONTIDjE. 



The lapillus in Neoceratodus fosteri (fig. 1), the "Bur- 

 nett Salmon " of Queensland, Australia, is of good size, 



* See Jour. Linn. Soc. vol. ix. No. 35, January, 1867. 

 f Illustrated in ' Zoologist,' January, 1915. 

 Zool. 4th ser. vol. XIX., July, 1915. x 



