128 MR. WOODWAKD ON SKI.ACHIAN MORPHOLOGY. [Feb. 21, 



pubic cartilage in its median portion is straight and narrow, but 

 l)ecomes slightly broader and is angularly bent backwards at about 

 one fourth of its total length from either extremity. From each 

 an<:ii!alion in front there projet'tf forward a very long tapering pre- 

 pnbic ))rocess, rightly interpreted as such by Sir Philip Egerton in 

 his original description of the fossil ; and immediately in advance of 

 the point of attachment of the basal cartilage of the pelvic fin on each 

 side another larger pnicess is seen to extend laterally. This is 

 almost or quite as broad as the median portion of the pubic cartilage 

 itself, and is directed outwards, without apparent tapering, to a 

 distance equal to the entire transverse extent of the complete pubic 

 element, when it bends backwards almost at right angles, and is half 



Pelvic eai-tilage of Ci/clohafis oUffodcu-fi/lus, from the Chalk of Mount Lebanon, 

 Syria. bp, basal cartilage of pelvic lin ; if, iliac iwocess ; ^jA, pubic 

 cartilage ; p.2Jl', prepubic process. 



as long again, though rapidly narrowed to a point. This remarkable 

 process was described by Egerton as the "proximal digit" of the 

 pelvic fin, while Mr. J. W. Davis has recently^ hazarded the 

 sugzestion that it " may have been the basal portion of a clasper." 

 As, however, no sutural line can be observed at the origin of the 

 cartilage, and as it is sometimes seen to be dorsalhj placed with 

 respect to the other structures, there cannot be much doubt that it 

 is the homologue of the well-known process named the iliac. 



The enormous proportions of these processes in Cyclobatis appears 

 at present inexplicable, the prepubic equalling no less than one 

 sixth the entire length of the disk. No known Selachian, so far as 

 I am aware, exhibits pelvic-arch processes of equal relative size, and 

 in tiie living Trygon these are comparatively insignificant or absent ". 



1 J. W. Davis, " Fossil Fishes of Chalk of Mount Lebanon," Trans. Eoy. 

 Dublin Soc. [2], vol iii. 1887, p. 4'JL>. 



^ In the figure of the skeleton of Triiijon given by Agassiz (' Rech. Poiss. 

 Fos8.' vol. iii. pi. n. fig. 1), a large ascending process is shown connecting the 

 pelvic cartilage with the vertebral column. This must be a:i artist's error. 



