Notes on the British Species o/" Lepadogaster. 10 L 



slender. As the larvae gradually assume the specific 

 characters, the lower rays of the ventrals appear to undergo 

 a partial atrophy, and assume the relative length characteristic 

 of the adult (c/. PI. VL, Figs. 3 and 4). 



The period at which the various barbels are developed 

 appears to correspond with the order of their phylogenetic 

 origin. The first to appear is that on the lower jaw, and 

 a stage is thus reached which represents the adult condition 

 in many Gadidae. This barbel is as yet undeveloped in 

 larv?e of Motella cimhria, 9 mm. long; it was first noticed as 

 a distinct papilla in larvae of 11 mm. The two lateral 

 barbels of the snout are next developed, and in the species 

 under consideration arise as small papilhe, which were first 

 noticed in larvce of 12*5 mm. This stage represents the 

 adult condition in Motella tricirrata and Motella macroi)h- 

 thalma. Finally the median barbel of the snout is recognis- 

 able as a faint tubercle in larv?e of 20 mm., and is well 

 marked in larvae of 30 mm. Thus the adult condition is 

 reached, and it is only after the formation of this fourth 

 barbel that the identity of the species is established. 



Explanation of Plate VI. 



Fig. 1. Larvae oi Motella cimhria, 5*3 mm. long ; lateral view. 



Fig. 2. The same specimen seen from above. 



Fig. 3. Later larvae 17 "5 mm. long, showing reduction in the larval 

 ventrals and the barbel on the lower jaw. 



Fig. 4. Young Motella cimhria., 31 '5 mm. long, showing the specific 

 characters. 



XVIII. Notes on the British Species of Lepadogaster, and on 

 the Development of the Vertical Fins. By Geoege Biiook, 

 Esq., r.L.S., F.R.S.E. [Plate VIL] 



(Read 18th April 1888.) 



It has long been admitted that the species of Lepadogaster 



are subject to considerable variation, particularly in colour, 



and a number of forms described as distinct are now regarded 



merely as varieties. Day, in his work on the " Fishes of Great 



Britain and Ireland," recognises only three species. He says 

 vol. X. L 



