1886.] ON SQUALORAJA POLYSPONDYLA. 527 



body (Plate LTI. fig. 1) in a later stage. Lettering as iu last 

 plate. 

 Fig. 7, 8. Transverse sections through a portion of outer surface of multicel- 

 lular body in a later stage, a, degenerating nuclei ; other lettering 

 as before. 

 9. Multicellular body from ovum of Protopterus, differing from that 

 illustrated in fig. 1 mainly by the absence of follicular layer. 

 Lettering as before. 



10. Portion of secondary follicular layer at point marked with an arrow 



in preceding figure ; more highly magnified. 



11. Central mass of a body belonging to same stage as that figured in fig. 9, 



to show the mass (j)) formed by the breaking down of the central 

 cells (e), the nuclei of which («) are here and there imbedded in it. 



12. One of central cells (Plate LII. fig. l,c) with a large number of 



nuclei. 



13. Three central cells from Stage I. (fig. 1, b), to show difference in 



nuclei. 

 14-20. Central cells very much enlarged from Plate LII. fig. 1, to show 



the different stages in degeneration of nuclei. 

 21. Nest of germinal cells in ovary of Ccratodus at a later stage than that 



in Plate LII. fig. 3. Lettering ns in that figure. 



Pl.\te LIV. 



Fig. 22. A portion of body represented in Plate LIII. fig. 21, more highly 

 magnified. Lettering as in fig. 21. 



23. Nest of germinal cells in ovary of Ceratodus at a stage near to that 



represented in figs. 21 and 22. Lettering as in those figures. 



24. Portion of multicellular bod}' in ovary of Protojiterus, to show masses 



of yolk {a), apparently corresponding to areas occupied by fused 

 masses of protoplasm in earlier stages (p in figs. 1, 9, and 11). 



25. Multicellular body of Ceratodus at a stage corresponding to that of 



Pro!'(9p('CT'«*, illustrated in fig. 1. a, fibrous tissue of stroma-layer ; 

 other lettering as in fig. 1. 



26. A portion of central cells of multicellular body of Ceratodats, more 



highly magnified. Lettering as in fig. 1. 

 27-31. Central cells of multicellular body of Protopterus at an early stage, 



to show commencing yolk. 

 32, 33. Central cells of ditto, to show disintegrating nucleus. 



2. On the Anatomy and Systematic Position of the Liassic 

 Selachian, Squaloraja polyspondyla, Agassiz. By A. 

 Smith Woodward, F.G.S., of the British Museum 

 (Natural History). 



[Eeceived October 18, 1886.] 

 (Plate LV.) 



Summary of Previous Researches. 



The prolific fish-beds of the Liassic formation have yielded so 

 much valuable material during recent years, that it is now possible 

 to considerably supplement the original anatomical memoirs of 

 Agassiz, Egerton, and the other pioneers in early Mesozoic ichthy- 

 ology. Many specific types that were at first only known from very 



