J 894.] CUEYATUEE OF THE SPIKE IN FISHES. 97 



total length, in this specimen it is nearly grd of that \ The hsemal 

 and neural arches of this specimen are normal, except for a marked 

 flexion forwards of the neurals numbering 20 to 24. 



Another instance of curvature of the spine in the Sole, for 

 which I am indebted to the Royal College of Surgeons, is that 

 traced in fig. 2. This ease differs most conspicuously from both 

 the foregoing in the acuteness of the first two sinuosities, and 

 in the fact that at each vertex there is a slight displacement to 

 the left side, which in all probability involved the body as a whole. 

 Except for the first eight neurals, which are very aberrant, the 

 arches had so adapted themselves to the situation as to have 

 maintained the normal regularity of contour of their extremities ; 

 and the only lesser detail worthy of remark here is the presence 

 of synostotic enlargements 2 on the neural spines 9, 10, and 11. 



48 vertebra? in all are present. 



Synostosis of the vertebrae of fishes has been recorded by Erdl 

 and Stannius 3 . While it is most generally regarded as confined to 

 the opposite extremities of the spine, Owen has pointed out 4 that 

 in Plewonectidce " a kind of sacrum is formed by such bony union 

 of the bodies of the fii'st two of the caudal series." Examination 

 of a series of Pleuronectid skeletons will easily convince anyone 

 that this is an inconstant feature. 



The most important monograph on the subject is to be found 

 among Hyrtl's classical contributions to the Vienna Denkschriften 5 . 

 In a short preliminary communication which immediately pre- 

 ceded the aforesaid monograph, Hyrtl remarked 6 that "the 

 number of co-ossified vertebrae is 2 to 6," and that " this synostosis 

 takes place more frequently in the tail than in the trunk " — while, 

 commenting on the probable ill effects of the malformation, he 

 naively points out that diminution in flexibility is, at any rate in 

 some cases, " obviated by the fact that the confluent vertebrae are 

 not larger than the non-confluent ones, their length being so much 

 reduced that the five coalesced vertebrae are not longer than one 

 and a slight fraction of a non-coalesced one." In his second 

 monograph he has described certain conditions to which this 

 fascinating argument will not apply, for example that of a Codfish 

 in which the six co-ossified vertebrae occupy a greater area than the 

 two which precede them. 



One of the aforementioned specimens which Prof. Sutton has 



1 Length 8| in., greatest vertical diameter 2| in. 



2 I have in no iustance observed these on the hsemal side. 



3 By Stannius in Amia (Handb. d. Zootomie, Aufl. 2, Th. i. p. 21). His 

 record of the fusion of "intercalary with true vertebrae" becomes one of 

 synostosis of vertebral bodies, from Schmidt's discovery (Zeitschr. wiss. Zool. 

 lid. liv. p. 748) of the truly vertebral nature of the so-called inter-centra of 

 this animal. 



4 Comp. Anat. of Vertebrates, vol. i. p. 42. 



5 " Ueb. Wirbelsynostosen und Wirbelsuturen bei Fischen," Wien. Denkschr. 

 xx. 1862, pp. 95-110. 



6 Nat. Hist. Keview, vol. ii. 1862, pp. 103-104. 



Peoo. Zool. Soc— 1894, No. VII. 7 



