198 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



plane and which are not connected with the shafts of the 

 axonosts, whilst the other four (the " elevators and depres- 

 sors ") are arranged 2 on each side, the anterior right and 

 left pair arising from the anterior surface of the fin ray 

 and being inserted into the lamina on the shaft of the 

 axonost in front of the median spine, the posterior pair 

 arising from the posterior surface of the ray and being 

 inserted into the posterior lamina. The latter muscles 

 elevate and depress the fin ray in the median plane. 



If the dorsal surface of the cranium cf a plaice be 

 examined, there will be noticed in the pseudo-mesial plane 

 a longitudinal trench-like depression which passes back- 

 wards in a slight sigmoid curve from left to right on the 

 left frontal and supraoccipital. This depression (see fig. 

 1) is connected with the extension forwards of the dorsal 

 fin over the roof of the cranium. Into it fit usually 

 axonosts 6, 7, 8, whilst the axonosts in front of these, 

 though too short to actually reach the cranium, are con- 

 nected with the depression by means of ligaments. 

 Behind the attachment of the eighth axonost, the occiput 

 suddenly shelves down, and in this depression, i.e., 

 bounded in front by the reduced occipital spine and 

 behind by the first neural spine, are situated the two suc- 

 ceeding axonosts (9 and 10). Behind the 10th the 

 axonosts become related to the neural spines as usual. 



The posterior extremity of the dorsal fin is only note- 

 worthy in two respects : (a) in the presence of 4 axonosts 

 between neural spines 36-37, the largest number found 

 between any two succeeding neural or haemal spines, 

 excepting the anterior extremity of the anal fin ; (b) the 

 last fin ray (71) articulates directly with the axonost (70) 

 without the intervention of a baseost. The last four 

 vertebrae have no connection either with the dorsal or anal 

 fins. In the specimen on which the above description was 



