296 THE ZOOLOGIST. 



frequents salt waters, the Salmon spends its life alternately in 

 salt and in fresh water, whilst the Grayling lives in fresh water 

 only. Comparing the three, the fresh-water fish has the largest 

 otolith, but they are all fairly large. 



Except with Arins gagora (Plate I. fig. 19), where it is on the 

 right, the big rounded stone, the lapillus is always on the left, the 

 asteriscus on the right, and the sagitta in the middle under the 

 other two. The upper set are always from the right half of the 

 head, and the lower set from the left side. In some cases the 

 smaller otoliths were not got, and consequently are not shown. 



Except those on Plate I. (figs. 16 and 19), and those on Plate II. 

 (figs. 3, 4, 5, and 7), all the figures shown are examples of fish that 

 have the sagitta as the largest of the three otoliths, in any one 

 half of the skull ; the examples are all from Teleostean fishes, with 

 the exception of figs. 5 and 6 on Plate II. The exceptions are 

 (Plate I. fig. 16) taken from a Carp (Cyprinus carpio), an example 

 of the class of fish where the asteriscus is the largest otolith,* the 

 sagitta being represented by a rod-like stone ; Plate I., fig. 19, 

 representing the otoliths of an Arius gagora, only those from one 

 side of the head are shown ; a member of the large family of 

 Siluroid fishes illustrates the case where the lapillus is the 

 largest otolith — it is seen on the right in the plate; in these 

 fishes also the sagitta takes on the rod-like form. Figs. 3 and 4 

 on Plate II., both from Siluroid fishes, shows the same. In the 

 family of the Characinidce we have another repetition ; it is shown 

 on Plate II. fig. 7. In the otoliths from Polypterus senegalus 

 (Plate II. fig. 5) is shown the example of a fish which has the 

 asteriscus as the largest otolith, but in which the sagitta is not 

 rod-like. The same occurs with the otoliths of Calamichthys 

 calabaricus and Amia calva. In Lepidosteus osseus (Plate II. 

 fig. 6) the sagitta is the largest of the three otoliths. The above 

 four fishes are all of an early type ; they are of the Ganoid order. 

 Three of them differ from the fourth in the manner noted. 



On Plate I., figs. 17 and 18, are shown otoliths from two of the 

 Scianidce ; fig. 17 from Otolithus maculatus, a fish from the Indian 

 Ocean ; and fig. 18 from Plagioscion surinamensis, a fresh-water 

 Scisenoid from British Guiana. Each shows the granular con- 



* This peculiarity of the asteriscus and lapillus was described in the 

 paper on " The ' Asteriscus ' in Fishes," ' Zoologist ' {ante, p. 57). 



