1010.] CAUDAL FIN OF THE TELEOSTOMT. 015 



two species. In the Liverpool Biological Coiniiiittce Momoii- on 

 the Plaice, Cole snjs, on p. 50: — "In the last distinct vertehni, 

 {i.e. the penultimate vertebra) it will he seen tl);it the neurnl 

 spine resembles the hjomal spine in strucl-ure, but that both are 

 peculiar. Each consists of a pai-tly cartilaginous shaft behind 

 iuid a thin laminate portion in front. The posterior shafts so 

 closely I'esemble the succeeding epural (i. e. dorsal caudal radial) 

 and hypiu'al [i. e. ventral caudal radial) bones respectively as to 

 siujyest that an epural above a,nd a hypttral below have fused on to 

 the laminate portions, which latter are undoubtedly similar to and 

 perhaps lepresent the neural and hfemal spines in front. As, 

 however, we have no positive evidence of such a fusion, the spines 

 in question are here described as simple neural and hfemal 

 spines." Though in Solea lutea this point is not so obvious as in 

 Fleuronectes, there is to be seen a distinct fusion line running 

 transversely across the proximal part of the epural, so that a 

 parallelism does occur between the two species. I take it that 

 Cole reserves committance on the subject on the ground that 

 actual fusion has not been observed during development ; but it 

 is scarcely to be expected that such a minute featm'e as the fusion 

 of a radial with a neural or hfemal spine will be recapitulated in 

 development, so that lack of embryological evidence would not 

 be fatal to the theory. But we have seen in the case of Box salpa 

 that such a fusion can be traced in development ; had Cole been 

 accpiainted with this as well as numerous other examples i-e- 

 sendiling that of the Plaice, he doubtless would have considered 

 these epurals and hypurals more than mei-e neural and hcemal 

 spines. 



To complete the description of the caudal fin of Solea, there 

 a,re two dorsal caudal radials (d.c.r.) between the epural and 

 hypuial bones ; in the corresponding position ventrally there is 

 a ventral caudal i-adial (v.c.r.). The last centrum bears a neural 

 arch (n.a.) which is not, as may be at first supposed, a urostyje, 

 since the spinal cord (sp.c.) passes through it, in the fashion of 

 other neural arches, in its course along the dorsal edge of the 

 last liypural. 



The caudal fin, then, is a homocercal type of an advanced 

 nature. It may be mentioned that other species of Solea, e. g. 

 S. monochir and S. impar, differ from aS'. lutea only in the number 

 of terminal hypurals and the extent of their collateral fusion. 



GoBius PAGANELLUS. (Gobiifomies, Gobiida\) (Plate L. 

 fig. 25.) 



The urostyle (ur.) is greatly reduced, and almost non-existent 

 and fused with the last hypural bone. There are thi-ee hypurals, 

 the last two, the largest, being fused to the last vertebral seg- 

 ment. A small trace of neural arch is present on the last 

 centrum and that of the penultimate is also reduced. Dorsally 

 thei'c are two caudal radials (d.c.r.) and ventndly one {v.c.r.). tlie 

 latter lying between the first and second hypurals. The spinal 



