( 131 ) 



ON THE LOCATION OF THE SACCULUS AND ITS 

 CONTAINED OTOLITHS IN FISHES. 



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



(Concluded from p. 109.) 

 OSTARIOPHYSI. 



In this suborder the families of the Characinidce, the Gymno- 

 tidce, the Cyprinidce, and the Aspredinidce have the asteriscus as 

 the largest otolith. In the families of the Siluridce and the 

 Loricariidce the lapillus is the largest. In all the families the 

 sagitta is rod-like, or perhaps would be better described as like 

 a splinter. 



ChARACINIDjE. 



The sacculus in this family is thoroughly embedded in a bony 



cavity which has to be carefully split open to expose it ; it is 



found completely filling the cavity. In Erythrinus salmoneus 



(fig. II., 5) the position of the sacculus is indicated from the 



outside by two polished-looking little excrescences of the basi- 



occiput. Macrodon trahira (the " Haimara " of British Guiana) 



has similar excrescences, the bone of them being very thin 



(fig. II., 6). Myletes setiger (the "Paca" of British Guiana) does 



not show these excrescences. The lapillus in this family is well 



developed, and lies in a special cavity at the side of the skull, 



but not showing palpably on the outside. Leporinus arcus 



and L. maculatus show their sagittse through the thin bone 



underlying them, which, however, lies flat and does not stand 



out at all. 



Gymnotid^:. 



Of this family only two small specimens have been available 

 for examination — one a Eigenmanuia virescens, the other a 

 Sternopygus macrurus ; they were too small to allow of any 

 external indications being noted. The asterisci were found to be 

 the largest of the otoliths. 



